/**
 *  A fragment is a single item from an ABI, which may represent any of:
 *
 *  - [Functions](FunctionFragment)
 *  - [Events](EventFragment)
 *  - [Constructors](ConstructorFragment)
 *  - Custom [Errors](ErrorFragment)
 *  - [Fallback or Receive](FallbackFragment) functions
 *
 *  @_subsection api/abi/abi-coder:Fragments  [about-fragments]
 */

import { defineProperties, getBigInt, getNumber, assert, assertPrivate, assertArgument } from 'ethers';
import { id } from 'ethers';

/**
 *  A Type description in a [JSON ABI format](link-solc-jsonabi).
 */
export interface JsonFragmentType {
    /**
     *  The parameter name.
     */
    readonly name?: string;

    /**
     *  If the parameter is indexed.
     */
    readonly indexed?: boolean;

    /**
     *  The type of the parameter.
     */
    readonly type?: string;

    /**
     *  The internal Solidity type.
     */
    readonly internalType?: string;

    /**
     *  The components for a tuple.
     */
    readonly components?: ReadonlyArray<JsonFragmentType>;
}

/**
 *  A fragment for a method, event or error in a [JSON ABI format](link-solc-jsonabi).
 */
export interface JsonFragment {
    /**
     *  The name of the error, event, function, etc.
     */
    readonly name?: string;

    /**
     *  The type of the fragment (e.g. ``event``, ``"function"``, etc.)
     */
    readonly type?: string;

    /**
     *  If the event is anonymous.
     */
    readonly anonymous?: boolean;

    /**
     *  If the function is payable.
     */
    readonly payable?: boolean;

    /**
     *  If the function is constant.
     */
    readonly constant?: boolean;

    /**
     *  The mutability state of the function.
     */
    readonly stateMutability?: string;

    /**
     *  The input parameters.
     */
    readonly inputs?: ReadonlyArray<JsonFragmentType>;

    /**
     *  The output parameters.
     */
    readonly outputs?: ReadonlyArray<JsonFragmentType>;

    /**
     *  The gas limit to use when sending a transaction for this function.
     */
    readonly gas?: string;
}

/**
 *  The format to serialize the output as.
 *
 *  **``"sighash"``** - the bare formatting, used to compute the selector
 *  or topic hash; this format cannot be reversed (as it discards ``indexed``)
 *  so cannot by used to export an [[Interface]].
 *
 *  **``"minimal"``** - Human-Readable ABI with minimal spacing and without
 *  names, so it is compact, but will result in Result objects that cannot
 *  be accessed by name.
 *
 *  **``"full"``** - Full Human-Readable ABI, with readable spacing and names
 *  intact; this is generally the recommended format.
 *
 *  **``"json"``** - The [JSON ABI format](link-solc-jsonabi).
 */
export type FormatType = 'sighash' | 'minimal' | 'full' | 'json';

// [ "a", "b" ] => { "a": 1, "b": 1 }
function setify(items: Array<string>): ReadonlySet<string> {
    const result: Set<string> = new Set();
    items.forEach((k) => result.add(k));
    return Object.freeze(result);
}

// Visibility Keywords
const _kwVisib = 'constant external internal payable private public pure view';
const KwVisib = setify(_kwVisib.split(' '));

const _kwTypes = 'constructor error event fallback function receive struct';
const KwTypes = setify(_kwTypes.split(' '));

const _kwModifiers = 'calldata memory storage payable indexed';
const KwModifiers = setify(_kwModifiers.split(' '));

const _kwOther = 'tuple returns';

// All Keywords
const _keywords = [_kwTypes, _kwModifiers, _kwOther, _kwVisib].join(' ');
const Keywords = setify(_keywords.split(' '));

// Single character tokens
const SimpleTokens: Record<string, string> = {
    '(': 'OPEN_PAREN',
    ')': 'CLOSE_PAREN',
    '[': 'OPEN_BRACKET',
    ']': 'CLOSE_BRACKET',
    ',': 'COMMA',
    '@': 'AT',
};

// Parser regexes to consume the next token
const regexWhitespacePrefix = new RegExp('^(\\s*)');
const regexNumberPrefix = new RegExp('^([0-9]+)');
const regexIdPrefix = new RegExp('^([a-zA-Z$_][a-zA-Z0-9$_]*)');

// Parser regexs to check validity
const regexId = new RegExp('^([a-zA-Z$_][a-zA-Z0-9$_]*)$');
const regexType = new RegExp('^(trcToken|address|bool|bytes([0-9]*)|string|u?int([0-9]*))$');

/**
 *  @ignore:
 */
type Token = Readonly<{
    // Type of token (e.g. TYPE, KEYWORD, NUMBER, etc)
    type: string;

    // Offset into the original source code
    offset: number;

    // Actual text content of the token
    text: string;

    // The parenthesis depth
    depth: number;

    // If a parenthesis, the offset (in tokens) that balances it
    match: number;

    // For parenthesis and commas, the offset (in tokens) to the
    // previous/next parenthesis or comma in the list
    linkBack: number;
    linkNext: number;

    // If a BRACKET, the value inside
    value: number;
}>;

class TokenString {
    #offset: number;
    #tokens: ReadonlyArray<Token>;

    get offset(): number {
        return this.#offset;
    }
    get length(): number {
        return this.#tokens.length - this.#offset;
    }

    constructor(tokens: ReadonlyArray<Token>) {
        this.#offset = 0;
        this.#tokens = tokens.slice();
    }

    clone(): TokenString {
        return new TokenString(this.#tokens);
    }
    reset(): void {
        this.#offset = 0;
    }

    #subTokenString(from = 0, to = 0): TokenString {
        return new TokenString(
            this.#tokens.slice(from, to).map((t) => {
                return Object.freeze(
                    Object.assign({}, t, {
                        match: t.match - from,
                        linkBack: t.linkBack - from,
                        linkNext: t.linkNext - from,
                    })
                );
            })
        );
    }

    // Pops and returns the value of the next token, if it is a keyword in allowed; throws if out of tokens
    popKeyword(allowed: ReadonlySet<string>): string {
        const top = this.peek();
        if (top.type !== 'KEYWORD' || !allowed.has(top.text)) {
            throw new Error(`expected keyword ${top.text}`);
        }
        return this.pop().text;
    }

    // Pops and returns the value of the next token if it is `type`; throws if out of tokens
    popType(type: string): string {
        if (this.peek().type !== type) {
            throw new Error(`expected ${type}; got ${JSON.stringify(this.peek())}`);
        }
        return this.pop().text;
    }

    // Pops and returns a "(" TOKENS ")"
    popParen(): TokenString {
        const top = this.peek();
        if (top.type !== 'OPEN_PAREN') {
            throw new Error('bad start');
        }
        const result = this.#subTokenString(this.#offset + 1, top.match + 1);
        this.#offset = top.match + 1;
        return result;
    }

    // Pops and returns the items within "(" ITEM1 "," ITEM2 "," ... ")"
    popParams(): Array<TokenString> {
        const top = this.peek();

        if (top.type !== 'OPEN_PAREN') {
            throw new Error('bad start');
        }

        const result: Array<TokenString> = [];

        while (this.#offset < top.match - 1) {
            const link = this.peek().linkNext;
            result.push(this.#subTokenString(this.#offset + 1, link));
            this.#offset = link;
        }

        this.#offset = top.match + 1;

        return result;
    }

    // Returns the top Token, throwing if out of tokens
    peek(): Token {
        if (this.#offset >= this.#tokens.length) {
            throw new Error('out-of-bounds');
        }
        return this.#tokens[this.#offset];
    }

    // Returns the next value, if it is a keyword in `allowed`
    peekKeyword(allowed: ReadonlySet<string>): null | string {
        const top = this.peekType('KEYWORD');
        return top != null && allowed.has(top) ? top : null;
    }

    // Returns the value of the next token if it is `type`
    peekType(type: string): null | string {
        if (this.length === 0) {
            return null;
        }
        const top = this.peek();
        return top.type === type ? top.text : null;
    }

    // Returns the next token; throws if out of tokens
    pop(): Token {
        const result = this.peek();
        this.#offset++;
        return result;
    }

    toString(): string {
        const tokens: Array<string> = [];
        for (let i = this.#offset; i < this.#tokens.length; i++) {
            const token = this.#tokens[i];
            tokens.push(`${token.type}:${token.text}`);
        }
        return `<TokenString ${tokens.join(' ')}>`;
    }
}

type Writeable<T> = { -readonly [P in keyof T]: T[P] };

function lex(text: string): TokenString {
    const tokens: Array<Token> = [];

    const throwError = (message: string) => {
        const token = offset < text.length ? JSON.stringify(text[offset]) : '$EOI';
        throw new Error(`invalid token ${token} at ${offset}: ${message}`);
    };

    const brackets: Array<number> = [];
    const commas: Array<number> = [];

    let offset = 0;
    while (offset < text.length) {
        // Strip off any leading whitespace
        let cur = text.substring(offset);
        let match = cur.match(regexWhitespacePrefix);
        if (match) {
            offset += match[1].length;
            cur = text.substring(offset);
        }

        const token = {
            depth: brackets.length,
            linkBack: -1,
            linkNext: -1,
            match: -1,
            type: '',
            text: '',
            offset,
            value: -1,
        };
        tokens.push(token);

        const type = SimpleTokens[cur[0]] || '';
        if (type) {
            token.type = type;
            token.text = cur[0];
            offset++;

            if (type === 'OPEN_PAREN') {
                brackets.push(tokens.length - 1);
                commas.push(tokens.length - 1);
            } else if (type == 'CLOSE_PAREN') {
                if (brackets.length === 0) {
                    throwError('no matching open bracket');
                }

                token.match = brackets.pop() as number;
                (<Writeable<Token>>tokens[token.match]).match = tokens.length - 1;
                token.depth--;

                token.linkBack = commas.pop() as number;
                (<Writeable<Token>>tokens[token.linkBack]).linkNext = tokens.length - 1;
            } else if (type === 'COMMA') {
                token.linkBack = commas.pop() as number;
                (<Writeable<Token>>tokens[token.linkBack]).linkNext = tokens.length - 1;
                commas.push(tokens.length - 1);
            } else if (type === 'OPEN_BRACKET') {
                token.type = 'BRACKET';
            } else if (type === 'CLOSE_BRACKET') {
                // Remove the CLOSE_BRACKET
                let suffix = (tokens.pop() as Token).text;
                if (tokens.length > 0 && tokens[tokens.length - 1].type === 'NUMBER') {
                    const value = (tokens.pop() as Token).text;
                    suffix = value + suffix;
                    (<Writeable<Token>>tokens[tokens.length - 1]).value = getNumber(value);
                }
                if (tokens.length === 0 || tokens[tokens.length - 1].type !== 'BRACKET') {
                    throw new Error('missing opening bracket');
                }
                (<Writeable<Token>>tokens[tokens.length - 1]).text += suffix;
            }

            continue;
        }

        match = cur.match(regexIdPrefix);
        if (match) {
            token.text = match[1];
            offset += token.text.length;

            if (Keywords.has(token.text)) {
                token.type = 'KEYWORD';
                continue;
            }

            if (token.text.match(regexType)) {
                token.type = 'TYPE';
                continue;
            }

            token.type = 'ID';
            continue;
        }

        match = cur.match(regexNumberPrefix);
        if (match) {
            token.text = match[1];
            token.type = 'NUMBER';
            offset += token.text.length;
            continue;
        }

        throw new Error(`unexpected token ${JSON.stringify(cur[0])} at position ${offset}`);
    }

    return new TokenString(tokens.map((t) => Object.freeze(t)));
}

// Check only one of `allowed` is in `set`
function allowSingle(set: ReadonlySet<string>, allowed: ReadonlySet<string>): void {
    const included: Array<string> = [];
    for (const key in allowed.keys()) {
        if (set.has(key)) {
            included.push(key);
        }
    }
    if (included.length > 1) {
        throw new Error(`conflicting types: ${included.join(', ')}`);
    }
}

// Functions to process a Solidity Signature TokenString from left-to-right for...

// ...the name with an optional type, returning the name
function consumeName(type: string, tokens: TokenString): string {
    if (tokens.peekKeyword(KwTypes)) {
        const keyword = tokens.pop().text;
        if (keyword !== type) {
            throw new Error(`expected ${type}, got ${keyword}`);
        }
    }

    return tokens.popType('ID');
}

// ...all keywords matching allowed, returning the keywords
function consumeKeywords(tokens: TokenString, allowed?: ReadonlySet<string>): ReadonlySet<string> {
    const keywords: Set<string> = new Set();
    // eslint-disable-next-line no-constant-condition
    while (true) {
        const keyword = tokens.peekType('KEYWORD');

        if (keyword == null || (allowed && !allowed.has(keyword))) {
            break;
        }
        tokens.pop();

        if (keywords.has(keyword)) {
            throw new Error(`duplicate keywords: ${JSON.stringify(keyword)}`);
        }
        keywords.add(keyword);
    }

    return Object.freeze(keywords);
}

// ...all visibility keywords, returning the coalesced mutability
function consumeMutability(tokens: TokenString): 'payable' | 'nonpayable' | 'view' | 'pure' {
    const modifiers = consumeKeywords(tokens, KwVisib);

    // Detect conflicting modifiers
    allowSingle(modifiers, setify('constant payable nonpayable'.split(' ')));
    allowSingle(modifiers, setify('pure view payable nonpayable'.split(' ')));

    // Process mutability states
    if (modifiers.has('view')) {
        return 'view';
    }
    if (modifiers.has('pure')) {
        return 'pure';
    }
    if (modifiers.has('payable')) {
        return 'payable';
    }
    if (modifiers.has('nonpayable')) {
        return 'nonpayable';
    }

    // Process legacy `constant` last
    if (modifiers.has('constant')) {
        return 'view';
    }

    return 'nonpayable';
}

// ...a parameter list, returning the ParamType list
function consumeParams(tokens: TokenString, allowIndexed?: boolean): Array<ParamType> {
    return tokens.popParams().map((t) => ParamType.from(t, allowIndexed));
}

// ...a gas limit, returning a BigNumber or null if none
function consumeGas(tokens: TokenString): null | bigint {
    if (tokens.peekType('AT')) {
        tokens.pop();
        if (tokens.peekType('NUMBER')) {
            return getBigInt(tokens.pop().text);
        }
        throw new Error('invalid gas');
    }
    return null;
}

function consumeEoi(tokens: TokenString): void {
    if (tokens.length) {
        throw new Error(`unexpected tokens: ${tokens.toString()}`);
    }
}

const regexArrayType = new RegExp(/^(.*)\[([0-9]*)\]$/);

function verifyBasicType(type: string): string {
    const match = type.match(regexType);
    assertArgument(match, 'invalid type', 'type', type);
    if (type === 'uint') {
        return 'uint256';
    }
    if (type === 'int') {
        return 'int256';
    }

    if (match[2]) {
        // bytesXX
        const length = parseInt(match[2]);
        assertArgument(length !== 0 && length <= 32, 'invalid bytes length', 'type', type);
    } else if (match[3]) {
        // intXX or uintXX
        const size = parseInt(match[3] as string);
        assertArgument(size !== 0 && size <= 256 && size % 8 === 0, 'invalid numeric width', 'type', type);
    }

    return type;
}

// Make the Fragment constructors effectively private
const _guard = {};

/**
 *  When [walking](ParamType-walk) a [[ParamType]], this is called
 *  on each component.
 */
export type ParamTypeWalkFunc = (type: string, value: any) => any;

/**
 *  When [walking asynchronously](ParamType-walkAsync) a [[ParamType]],
 *  this is called on each component.
 */
export type ParamTypeWalkAsyncFunc = (type: string, value: any) => any | Promise<any>;

const internal = Symbol.for('_ethers_internal');

const ParamTypeInternal = '_ParamTypeInternal';
const ErrorFragmentInternal = '_ErrorInternal';
const EventFragmentInternal = '_EventInternal';
const ConstructorFragmentInternal = '_ConstructorInternal';
const FallbackFragmentInternal = '_FallbackInternal';
const FunctionFragmentInternal = '_FunctionInternal';
const StructFragmentInternal = '_StructInternal';

/**
 *  Each input and output of a [[Fragment]] is an Array of **ParamType**.
 */
export class ParamType {
    /**
     *  The local name of the parameter (or ``""`` if unbound)
     */
    readonly name!: string;

    /**
     *  The fully qualified type (e.g. ``"address"``, ``"tuple(address)"``,
     *  ``"uint256[3][]"``)
     */
    readonly type!: string;

    /**
     *  The base type (e.g. ``"address"``, ``"tuple"``, ``"array"``)
     */
    readonly baseType!: string;

    /**
     *  True if the parameters is indexed.
     *
     *  For non-indexable types this is ``null``.
     */
    readonly indexed!: null | boolean;

    /**
     *  The components for the tuple.
     *
     *  For non-tuple types this is ``null``.
     */
    readonly components!: null | ReadonlyArray<ParamType>;

    /**
     *  The array length, or ``-1`` for dynamic-lengthed arrays.
     *
     *  For non-array types this is ``null``.
     */
    readonly arrayLength!: null | number;

    /**
     *  The type of each child in the array.
     *
     *  For non-array types this is ``null``.
     */
    readonly arrayChildren!: null | ParamType;

    /**
     *  @private
     */
    constructor(
        guard: any,
        name: string,
        type: string,
        baseType: string,
        indexed: null | boolean,
        components: null | ReadonlyArray<ParamType>,
        arrayLength: null | number,
        arrayChildren: null | ParamType
    ) {
        assertPrivate(guard, _guard, 'ParamType');
        Object.defineProperty(this, internal, { value: ParamTypeInternal });

        if (components) {
            components = Object.freeze(components.slice());
        }

        if (baseType === 'array') {
            if (arrayLength == null || arrayChildren == null) {
                throw new Error('');
            }
        } else if (arrayLength != null || arrayChildren != null) {
            throw new Error('');
        }

        if (baseType === 'tuple') {
            if (components == null) {
                throw new Error('');
            }
        } else if (components != null) {
            throw new Error('');
        }

        defineProperties<ParamType>(this, {
            name,
            type,
            baseType,
            indexed,
            components,
            arrayLength,
            arrayChildren,
        });
    }

    /**
     *  Return a string representation of this type.
     *
     *  For example,
     *
     *  ``sighash" => "(uint256,address)"``
     *
     *  ``"minimal" => "tuple(uint256,address) indexed"``
     *
     *  ``"full" => "tuple(uint256 foo, address bar) indexed baz"``
     */
    format(format?: FormatType): string {
        if (format == null) {
            format = 'sighash';
        }
        if (format === 'json') {
            const result: any = {
                type: this.baseType === 'tuple' ? 'tuple' : this.type,
                name: this.name || undefined,
            };
            if (typeof this.indexed === 'boolean') {
                result.indexed = this.indexed;
            }
            if (this.isTuple()) {
                result.components = this.components.map((c) => JSON.parse(c.format(format)));
            }
            return JSON.stringify(result);
        }

        let result = '';

        // Array
        if (this.isArray()) {
            result += this.arrayChildren.format(format);
            result += `[${this.arrayLength < 0 ? '' : String(this.arrayLength)}]`;
        } else {
            if (this.isTuple()) {
                if (format !== 'sighash') {
                    result += this.type;
                }
                result += '(' + this.components.map((comp) => comp.format(format)).join(format === 'full' ? ', ' : ',') + ')';
            } else {
                result += this.type;
            }
        }

        if (format !== 'sighash') {
            if (this.indexed === true) {
                result += ' indexed';
            }
            if (format === 'full' && this.name) {
                result += ' ' + this.name;
            }
        }

        return result;
    }

    /**
     *  Returns true if %%this%% is an Array type.
     *
     *  This provides a type gaurd ensuring that [[arrayChildren]]
     *  and [[arrayLength]] are non-null.
     */
    isArray(): this is ParamType & {
        arrayChildren: ParamType;
        arrayLength: number;
    } {
        return this.baseType === 'array';
    }

    /**
     *  Returns true if %%this%% is a Tuple type.
     *
     *  This provides a type gaurd ensuring that [[components]]
     *  is non-null.
     */
    isTuple(): this is ParamType & { components: ReadonlyArray<ParamType> } {
        return this.baseType === 'tuple';
    }

    /**
     *  Returns true if %%this%% is an Indexable type.
     *
     *  This provides a type gaurd ensuring that [[indexed]]
     *  is non-null.
     */
    isIndexable(): this is ParamType & { indexed: boolean } {
        return this.indexed != null;
    }

    /**
     *  Walks the **ParamType** with %%value%%, calling %%process%%
     *  on each type, destructing the %%value%% recursively.
     */
    walk(value: any, process: ParamTypeWalkFunc): any {
        if (this.isArray()) {
            if (!Array.isArray(value)) {
                throw new Error('invalid array value');
            }
            if (this.arrayLength !== -1 && value.length !== this.arrayLength) {
                throw new Error('array is wrong length');
            }
            return value.map((v) => this.arrayChildren?.walk(v, process));
        }

        if (this.isTuple()) {
            if (!Array.isArray(value)) {
                throw new Error('invalid tuple value');
            }
            if (value.length !== this.components.length) {
                throw new Error('array is wrong length');
            }
            return value.map((v, i) => this.components?.[i].walk(v, process));
        }

        return process(this.type, value);
    }

    #walkAsync(
        promises: Array<Promise<void>>,
        value: any,
        process: ParamTypeWalkAsyncFunc,
        setValue: (value: any) => void
    ): void {
        if (this.isArray()) {
            if (!Array.isArray(value)) {
                throw new Error('invalid array value');
            }
            if (this.arrayLength !== -1 && value.length !== this.arrayLength) {
                throw new Error('array is wrong length');
            }
            const childType = this.arrayChildren;

            const result = value.slice();
            result.forEach((value, index) => {
                childType.#walkAsync(promises, value, process, (value: any) => {
                    result[index] = value;
                });
            });
            setValue(result);
            return;
        }

        if (this.isTuple()) {
            const components = this.components;

            // Convert the object into an array
            let result: Array<any>;
            if (Array.isArray(value)) {
                result = value.slice();
            } else {
                if (value == null || typeof value !== 'object') {
                    throw new Error('invalid tuple value');
                }

                result = components.map((param) => {
                    if (!param.name) {
                        throw new Error('cannot use object value with unnamed components');
                    }
                    if (!(param.name in value)) {
                        throw new Error(`missing value for component ${param.name}`);
                    }
                    return value[param.name];
                });
            }

            if (result.length !== this.components.length) {
                throw new Error('array is wrong length');
            }

            result.forEach((value, index) => {
                components[index].#walkAsync(promises, value, process, (value: any) => {
                    result[index] = value;
                });
            });
            setValue(result);
            return;
        }

        const result = process(this.type, value);
        if (result.then) {
            promises.push(
                (async function () {
                    setValue(await result);
                })()
            );
        } else {
            setValue(result);
        }
    }

    /**
     *  Walks the **ParamType** with %%value%%, asynchronously calling
     *  %%process%% on each type, destructing the %%value%% recursively.
     *
     *  This can be used to resolve ENS naes by walking and resolving each
     *  ``"address"`` type.
     */
    async walkAsync(value: any, process: ParamTypeWalkAsyncFunc): Promise<any> {
        const promises: Array<Promise<void>> = [];
        const result: [any] = [value];
        this.#walkAsync(promises, value, process, (value: any) => {
            result[0] = value;
        });
        if (promises.length) {
            await Promise.all(promises);
        }
        return result[0];
    }

    /**
     *  Creates a new **ParamType** for %%obj%%.
     *
     *  If %%allowIndexed%% then the ``indexed`` keyword is permitted,
     *  otherwise the ``indexed`` keyword will throw an error.
     */
    static from(obj: any, allowIndexed?: boolean): ParamType {
        if (ParamType.isParamType(obj)) {
            return obj;
        }

        if (typeof obj === 'string') {
            return ParamType.from(lex(obj), allowIndexed);
        } else if (obj instanceof TokenString) {
            let type = '',
                baseType = '';
            let comps: null | Array<ParamType> = null;

            if (consumeKeywords(obj, setify(['tuple'])).has('tuple') || obj.peekType('OPEN_PAREN')) {
                // Tuple
                baseType = 'tuple';
                comps = obj.popParams().map((t) => ParamType.from(t));
                type = `tuple(${comps.map((c) => c.format()).join(',')})`;
            } else {
                // Normal
                type = verifyBasicType(obj.popType('TYPE'));
                baseType = type;
            }

            // Check for Array
            let arrayChildren: null | ParamType = null;
            let arrayLength: null | number = null;

            while (obj.length && obj.peekType('BRACKET')) {
                const bracket = obj.pop(); //arrays[i];
                arrayChildren = new ParamType(_guard, '', type, baseType, null, comps, arrayLength, arrayChildren);
                arrayLength = bracket.value;
                type += bracket.text;
                baseType = 'array';
                comps = null;
            }

            let indexed: boolean | null = null;
            const keywords = consumeKeywords(obj, KwModifiers);
            if (keywords.has('indexed')) {
                if (!allowIndexed) {
                    throw new Error('');
                }
                indexed = true;
            }

            const name = obj.peekType('ID') ? obj.pop().text : '';

            if (obj.length) {
                throw new Error('leftover tokens');
            }

            return new ParamType(_guard, name, type, baseType, indexed, comps, arrayLength, arrayChildren);
        }

        const name = obj.name;
        assertArgument(!name || (typeof name === 'string' && name.match(regexId)), 'invalid name', 'obj.name', name);

        let indexed = obj.indexed;
        if (indexed != null) {
            assertArgument(allowIndexed, 'parameter cannot be indexed', 'obj.indexed', obj.indexed);
            indexed = !!indexed;
        }

        let type = obj.type;

        const arrayMatch = type.match(regexArrayType);
        if (arrayMatch) {
            const arrayLength = parseInt(arrayMatch[2] || '-1');
            const arrayChildren = ParamType.from({
                type: arrayMatch[1],
                components: obj.components,
            });

            return new ParamType(_guard, name || '', type, 'array', indexed, null, arrayLength, arrayChildren);
        }

        if (type === 'tuple' || type.startsWith('tuple(' /* fix: ) */) || type.startsWith('(' /* fix: ) */)) {
            const comps = obj.components != null ? obj.components.map((c: any) => ParamType.from(c)) : null;
            const tuple = new ParamType(_guard, name || '', type, 'tuple', indexed, comps, null, null);
            // @TODO: use lexer to validate and normalize type
            return tuple;
        }

        type = verifyBasicType(obj.type);

        return new ParamType(_guard, name || '', type, type, indexed, null, null, null);
    }

    /**
     *  Returns true if %%value%% is a **ParamType**.
     */
    static isParamType(value: any): value is ParamType {
        return value && value[internal] === ParamTypeInternal;
    }
}

/**
 *  The type of a [[Fragment]].
 */
export type FragmentType = 'constructor' | 'error' | 'event' | 'fallback' | 'function' | 'struct';

/**
 *  An abstract class to represent An individual fragment from a parse ABI.
 */
export abstract class Fragment {
    /**
     *  The type of the fragment.
     */
    readonly type!: FragmentType;

    /**
     *  The inputs for the fragment.
     */
    readonly inputs!: ReadonlyArray<ParamType>;

    /**
     *  @private
     */
    constructor(guard: any, type: FragmentType, inputs: ReadonlyArray<ParamType>) {
        assertPrivate(guard, _guard, 'Fragment');
        inputs = Object.freeze(inputs.slice());
        defineProperties<Fragment>(this, { type, inputs });
    }

    /**
     *  Returns a string representation of this fragment as %%format%%.
     */
    abstract format(format?: FormatType): string;

    /**
     *  Creates a new **Fragment** for %%obj%%, wich can be any supported
     *  ABI frgament type.
     */
    static from(obj: any): Fragment {
        if (typeof obj === 'string') {
            // Try parsing JSON...
            try {
                Fragment.from(JSON.parse(obj));
            } catch (e) {
                //
            }

            // ...otherwise, use the human-readable lexer
            return Fragment.from(lex(obj));
        }

        if (obj instanceof TokenString) {
            // Human-readable ABI (already lexed)

            const type = obj.peekKeyword(KwTypes);

            switch (type) {
                case 'constructor':
                    return ConstructorFragment.from(obj);
                case 'error':
                    return ErrorFragment.from(obj);
                case 'event':
                    return EventFragment.from(obj);
                case 'fallback':
                case 'receive':
                    return FallbackFragment.from(obj);
                case 'function':
                    return FunctionFragment.from(obj);
                case 'struct':
                    return StructFragment.from(obj);
            }
        } else if (typeof obj === 'object') {
            // JSON ABI

            switch (obj.type) {
                case 'constructor':
                    return ConstructorFragment.from(obj);
                case 'error':
                    return ErrorFragment.from(obj);
                case 'event':
                    return EventFragment.from(obj);
                case 'fallback':
                case 'receive':
                    return FallbackFragment.from(obj);
                case 'function':
                    return FunctionFragment.from(obj);
                case 'struct':
                    return StructFragment.from(obj);
            }

            assert(false, `unsupported type: ${obj.type}`, 'UNSUPPORTED_OPERATION', {
                operation: 'Fragment.from',
            });
        }

        assertArgument(false, 'unsupported frgament object', 'obj', obj);
    }

    /**
     *  Returns true if %%value%% is a [[ConstructorFragment]].
     */
    static isConstructor(value: any): value is ConstructorFragment {
        return ConstructorFragment.isFragment(value);
    }

    /**
     *  Returns true if %%value%% is an [[ErrorFragment]].
     */
    static isError(value: any): value is ErrorFragment {
        return ErrorFragment.isFragment(value);
    }

    /**
     *  Returns true if %%value%% is an [[EventFragment]].
     */
    static isEvent(value: any): value is EventFragment {
        return EventFragment.isFragment(value);
    }

    /**
     *  Returns true if %%value%% is a [[FunctionFragment]].
     */
    static isFunction(value: any): value is FunctionFragment {
        return FunctionFragment.isFragment(value);
    }

    /**
     *  Returns true if %%value%% is a [[StructFragment]].
     */
    static isStruct(value: any): value is StructFragment {
        return StructFragment.isFragment(value);
    }
}

/**
 *  An abstract class to represent An individual fragment
 *  which has a name from a parse ABI.
 */
export abstract class NamedFragment extends Fragment {
    /**
     *  The name of the fragment.
     */
    readonly name!: string;

    /**
     *  @private
     */
    constructor(guard: any, type: FragmentType, name: string, inputs: ReadonlyArray<ParamType>) {
        super(guard, type, inputs);
        assertArgument(typeof name === 'string' && name.match(regexId), 'invalid identifier', 'name', name);
        inputs = Object.freeze(inputs.slice());
        defineProperties<NamedFragment>(this, { name });
    }
}

function joinParams(format: FormatType, params: ReadonlyArray<ParamType>): string {
    return '(' + params.map((p) => p.format(format)).join(format === 'full' ? ', ' : ',') + ')';
}

/**
 *  A Fragment which represents a //Custom Error//.
 */
export class ErrorFragment extends NamedFragment {
    /**
     *  @private
     */
    constructor(guard: any, name: string, inputs: ReadonlyArray<ParamType>) {
        super(guard, 'error', name, inputs);
        Object.defineProperty(this, internal, { value: ErrorFragmentInternal });
    }

    /**
     *  The Custom Error selector.
     */
    get selector(): string {
        return id(this.format('sighash')).substring(0, 10);
    }

    /**
     *  Returns a string representation of this fragment as %%format%%.
     */
    format(format?: FormatType): string {
        if (format == null) {
            format = 'sighash';
        }
        if (format === 'json') {
            return JSON.stringify({
                type: 'error',
                name: this.name,
                inputs: this.inputs.map((input) => JSON.parse(input.format(format))),
            });
        }

        const result: string[] = [];
        if (format !== 'sighash') {
            result.push('error');
        }
        result.push(this.name + joinParams(format, this.inputs));
        return result.join(' ');
    }

    /**
     *  Returns a new **ErrorFragment** for %%obj%%.
     */
    static from(obj: any): ErrorFragment {
        if (ErrorFragment.isFragment(obj)) {
            return obj;
        }

        if (typeof obj === 'string') {
            return ErrorFragment.from(lex(obj));
        } else if (obj instanceof TokenString) {
            const name = consumeName('error', obj);
            const inputs = consumeParams(obj);
            consumeEoi(obj);

            return new ErrorFragment(_guard, name, inputs);
        }

        return new ErrorFragment(_guard, obj.name, obj.inputs ? obj.inputs.map(ParamType.from) : []);
    }

    /**
     *  Returns ``true`` and provides a type guard if %%value%% is an
     *  **ErrorFragment**.
     */
    static isFragment(value: any): value is ErrorFragment {
        return value && value[internal] === ErrorFragmentInternal;
    }
}

/**
 *  A Fragment which represents an Event.
 */
export class EventFragment extends NamedFragment {
    /**
     *  Whether this event is anonymous.
     */
    readonly anonymous!: boolean;

    /**
     *  @private
     */
    constructor(guard: any, name: string, inputs: ReadonlyArray<ParamType>, anonymous: boolean) {
        super(guard, 'event', name, inputs);
        Object.defineProperty(this, internal, { value: EventFragmentInternal });
        defineProperties<EventFragment>(this, { anonymous });
    }

    /**
     *  The Event topic hash.
     */
    get topicHash(): string {
        return id(this.format('sighash'));
    }

    /**
     *  Returns a string representation of this event as %%format%%.
     */
    format(format?: FormatType): string {
        if (format == null) {
            format = 'sighash';
        }
        if (format === 'json') {
            return JSON.stringify({
                type: 'event',
                anonymous: this.anonymous,
                name: this.name,
                inputs: this.inputs.map((i) => JSON.parse(i.format(format))),
            });
        }

        const result: string[] = [];
        if (format !== 'sighash') {
            result.push('event');
        }
        result.push(this.name + joinParams(format, this.inputs));
        if (format !== 'sighash' && this.anonymous) {
            result.push('anonymous');
        }
        return result.join(' ');
    }

    /**
     *  Return the topic hash for an event with %%name%% and %%params%%.
     */
    static getTopicHash(name: string, params?: Array<any>): string {
        params = (params || []).map((p) => ParamType.from(p));
        const fragment = new EventFragment(_guard, name, params, false);
        return fragment.topicHash;
    }

    /**
     *  Returns a new **EventFragment** for %%obj%%.
     */
    static from(obj: any): EventFragment {
        if (EventFragment.isFragment(obj)) {
            return obj;
        }

        if (typeof obj === 'string') {
            return EventFragment.from(lex(obj));
        } else if (obj instanceof TokenString) {
            const name = consumeName('event', obj);
            const inputs = consumeParams(obj, true);
            const anonymous = !!consumeKeywords(obj, setify(['anonymous'])).has('anonymous');
            consumeEoi(obj);

            return new EventFragment(_guard, name, inputs, anonymous);
        }

        return new EventFragment(
            _guard,
            obj.name,
            obj.inputs ? obj.inputs.map((p: any) => ParamType.from(p, true)) : [],
            !!obj.anonymous
        );
    }

    /**
     *  Returns ``true`` and provides a type guard if %%value%% is an
     *  **EventFragment**.
     */
    static isFragment(value: any): value is EventFragment {
        return value && value[internal] === EventFragmentInternal;
    }
}

/**
 *  A Fragment which represents a constructor.
 */
export class ConstructorFragment extends Fragment {
    /**
     *  Whether the constructor can receive an endowment.
     */
    readonly payable!: boolean;

    /**
     *  The recommended gas limit for deployment or ``null``.
     */
    readonly gas!: null | bigint;

    /**
     *  @private
     */
    constructor(guard: any, type: FragmentType, inputs: ReadonlyArray<ParamType>, payable: boolean, gas: null | bigint) {
        super(guard, type, inputs);
        Object.defineProperty(this, internal, {
            value: ConstructorFragmentInternal,
        });
        defineProperties<ConstructorFragment>(this, { payable, gas });
    }

    /**
     *  Returns a string representation of this constructor as %%format%%.
     */
    format(format?: FormatType): string {
        assert(format != null && format !== 'sighash', 'cannot format a constructor for sighash', 'UNSUPPORTED_OPERATION', {
            operation: 'format(sighash)',
        });

        if (format === 'json') {
            return JSON.stringify({
                type: 'constructor',
                stateMutability: this.payable ? 'payable' : 'undefined',
                payable: this.payable,
                gas: this.gas != null ? this.gas : undefined,
                inputs: this.inputs.map((i) => JSON.parse(i.format(format))),
            });
        }

        const result = [`constructor${joinParams(format, this.inputs)}`];
        result.push(this.payable ? 'payable' : 'nonpayable');
        if (this.gas != null) {
            result.push(`@${this.gas.toString()}`);
        }
        return result.join(' ');
    }

    /**
     *  Returns a new **ConstructorFragment** for %%obj%%.
     */
    static from(obj: any): ConstructorFragment {
        if (ConstructorFragment.isFragment(obj)) {
            return obj;
        }

        if (typeof obj === 'string') {
            return ConstructorFragment.from(lex(obj));
        } else if (obj instanceof TokenString) {
            consumeKeywords(obj, setify(['constructor']));
            const inputs = consumeParams(obj);
            const payable = !!consumeKeywords(obj, setify(['payable'])).has('payable');
            const gas = consumeGas(obj);
            consumeEoi(obj);

            return new ConstructorFragment(_guard, 'constructor', inputs, payable, gas);
        }

        return new ConstructorFragment(
            _guard,
            'constructor',
            obj.inputs ? obj.inputs.map(ParamType.from) : [],
            !!obj.payable,
            obj.gas != null ? obj.gas : null
        );
    }

    /**
     *  Returns ``true`` and provides a type guard if %%value%% is a
     *  **ConstructorFragment**.
     */
    static isFragment(value: any): value is ConstructorFragment {
        return value && value[internal] === ConstructorFragmentInternal;
    }
}

/**
 *  A Fragment which represents a method.
 */
export class FallbackFragment extends Fragment {
    /**
     *  If the function can be sent value during invocation.
     */
    readonly payable!: boolean;

    constructor(guard: any, inputs: ReadonlyArray<ParamType>, payable: boolean) {
        super(guard, 'fallback', inputs);
        Object.defineProperty(this, internal, { value: FallbackFragmentInternal });
        defineProperties<FallbackFragment>(this, { payable });
    }

    /**
     *  Returns a string representation of this fallback as %%format%%.
     */
    format(format?: FormatType): string {
        const type = this.inputs.length === 0 ? 'receive' : 'fallback';

        if (format === 'json') {
            const stateMutability = this.payable ? 'payable' : 'nonpayable';
            return JSON.stringify({ type, stateMutability });
        }

        return `${type}()${this.payable ? ' payable' : ''}`;
    }

    /**
     *  Returns a new **FallbackFragment** for %%obj%%.
     */
    static from(obj: any): FallbackFragment {
        if (FallbackFragment.isFragment(obj)) {
            return obj;
        }

        if (typeof obj === 'string') {
            return FallbackFragment.from(lex(obj));
        } else if (obj instanceof TokenString) {
            const errorObj = obj.toString();

            const topIsValid = obj.peekKeyword(setify(['fallback', 'receive']));
            assertArgument(topIsValid, 'type must be fallback or receive', 'obj', errorObj);

            const type = obj.popKeyword(setify(['fallback', 'receive']));

            // receive()
            if (type === 'receive') {
                const inputs = consumeParams(obj);
                assertArgument(inputs.length === 0, `receive cannot have arguments`, 'obj.inputs', inputs);
                consumeKeywords(obj, setify(['payable']));
                consumeEoi(obj);
                return new FallbackFragment(_guard, [], true);
            }

            // fallback() [payable]
            // fallback(bytes) [payable] returns (bytes)
            let inputs = consumeParams(obj);
            if (inputs.length) {
                assertArgument(
                    inputs.length === 1 && inputs[0].type === 'bytes',
                    'invalid fallback inputs',
                    'obj.inputs',
                    inputs.map((i) => i.format('minimal')).join(', ')
                );
            } else {
                inputs = [ParamType.from('bytes')];
            }

            const mutability = consumeMutability(obj);
            assertArgument(
                mutability === 'nonpayable' || mutability === 'payable',
                'fallback cannot be constants',
                'obj.stateMutability',
                mutability
            );

            if (consumeKeywords(obj, setify(['returns'])).has('returns')) {
                const outputs = consumeParams(obj);
                assertArgument(
                    outputs.length === 1 && outputs[0].type === 'bytes',
                    'invalid fallback outputs',
                    'obj.outputs',
                    outputs.map((i) => i.format('minimal')).join(', ')
                );
            }

            consumeEoi(obj);

            return new FallbackFragment(_guard, inputs, mutability === 'payable');
        }

        if (obj.type === 'receive') {
            return new FallbackFragment(_guard, [], true);
        }

        if (obj.type === 'fallback') {
            const inputs = [ParamType.from('bytes')];
            const payable = obj.stateMutability === 'payable';
            return new FallbackFragment(_guard, inputs, payable);
        }

        assertArgument(false, 'invalid fallback description', 'obj', obj);
    }

    /**
     *  Returns ``true`` and provides a type guard if %%value%% is a
     *  **FallbackFragment**.
     */
    static isFragment(value: any): value is FallbackFragment {
        return value && value[internal] === FallbackFragmentInternal;
    }
}

/**
 *  A Fragment which represents a method.
 */
export class FunctionFragment extends NamedFragment {
    /**
     *  If the function is constant (e.g. ``pure`` or ``view`` functions).
     */
    readonly constant!: boolean;

    /**
     *  The returned types for the result of calling this function.
     */
    readonly outputs!: ReadonlyArray<ParamType>;

    /**
     *  The state mutability (e.g. ``payable``, ``nonpayable``, ``view``
     *  or ``pure``)
     */
    readonly stateMutability!: 'payable' | 'nonpayable' | 'view' | 'pure';

    /**
     *  If the function can be sent value during invocation.
     */
    readonly payable!: boolean;

    /**
     *  The recommended gas limit to send when calling this function.
     */
    readonly gas!: null | bigint;

    /**
     *  @private
     */
    constructor(
        guard: any,
        name: string,
        stateMutability: 'payable' | 'nonpayable' | 'view' | 'pure',
        inputs: ReadonlyArray<ParamType>,
        outputs: ReadonlyArray<ParamType>,
        gas: null | bigint
    ) {
        super(guard, 'function', name, inputs);
        Object.defineProperty(this, internal, { value: FunctionFragmentInternal });
        outputs = Object.freeze(outputs.slice());
        const constant = stateMutability === 'view' || stateMutability === 'pure';
        const payable = stateMutability === 'payable';
        defineProperties<FunctionFragment>(this, {
            constant,
            gas,
            outputs,
            payable,
            stateMutability,
        });
    }

    /**
     *  The Function selector.
     */
    get selector(): string {
        return id(this.format('sighash')).substring(0, 10);
    }

    /**
     *  Returns a string representation of this function as %%format%%.
     */
    format(format?: FormatType): string {
        if (format == null) {
            format = 'sighash';
        }
        if (format === 'json') {
            return JSON.stringify({
                type: 'function',
                name: this.name,
                constant: this.constant,
                stateMutability: this.stateMutability !== 'nonpayable' ? this.stateMutability : undefined,
                payable: this.payable,
                gas: this.gas != null ? this.gas : undefined,
                inputs: this.inputs.map((i) => JSON.parse(i.format(format))),
                outputs: this.outputs.map((o) => JSON.parse(o.format(format))),
            });
        }

        const result: string[] = [];

        if (format !== 'sighash') {
            result.push('function');
        }

        result.push(this.name + joinParams(format, this.inputs));

        if (format !== 'sighash') {
            if (this.stateMutability !== 'nonpayable') {
                result.push(this.stateMutability);
            }

            if (this.outputs && this.outputs.length) {
                result.push('returns');
                result.push(joinParams(format, this.outputs));
            }

            if (this.gas != null) {
                result.push(`@${this.gas.toString()}`);
            }
        }
        return result.join(' ');
    }

    /**
     *  Return the selector for a function with %%name%% and %%params%%.
     */
    static getSelector(name: string, params?: Array<any>): string {
        params = (params || []).map((p) => ParamType.from(p));
        const fragment = new FunctionFragment(_guard, name, 'view', params, [], null);
        return fragment.selector;
    }

    /**
     *  Returns a new **FunctionFragment** for %%obj%%.
     */
    static from(obj: any): FunctionFragment {
        if (FunctionFragment.isFragment(obj)) {
            return obj;
        }

        if (typeof obj === 'string') {
            return FunctionFragment.from(lex(obj));
        } else if (obj instanceof TokenString) {
            const name = consumeName('function', obj);
            const inputs = consumeParams(obj);
            const mutability = consumeMutability(obj);

            let outputs: Array<ParamType> = [];
            if (consumeKeywords(obj, setify(['returns'])).has('returns')) {
                outputs = consumeParams(obj);
            }

            const gas = consumeGas(obj);

            consumeEoi(obj);

            return new FunctionFragment(_guard, name, mutability, inputs, outputs, gas);
        }

        let stateMutability = obj.stateMutability;

        // Use legacy Solidity ABI logic if stateMutability is missing
        if (stateMutability == null) {
            stateMutability = 'payable';

            if (typeof obj.constant === 'boolean') {
                stateMutability = 'view';
                if (!obj.constant) {
                    stateMutability = 'payable';
                    if (typeof obj.payable === 'boolean' && !obj.payable) {
                        stateMutability = 'nonpayable';
                    }
                }
            } else if (typeof obj.payable === 'boolean' && !obj.payable) {
                stateMutability = 'nonpayable';
            }
        }

        // @TODO: verifyState for stateMutability (e.g. throw if
        //        payable: false but stateMutability is "nonpayable")

        return new FunctionFragment(
            _guard,
            obj.name,
            stateMutability,
            obj.inputs ? obj.inputs.map(ParamType.from) : [],
            obj.outputs ? obj.outputs.map(ParamType.from) : [],
            obj.gas != null ? obj.gas : null
        );
    }

    /**
     *  Returns ``true`` and provides a type guard if %%value%% is a
     *  **FunctionFragment**.
     */
    static isFragment(value: any): value is FunctionFragment {
        return value && value[internal] === FunctionFragmentInternal;
    }
}

/**
 *  A Fragment which represents a structure.
 */
export class StructFragment extends NamedFragment {
    /**
     *  @private
     */
    constructor(guard: any, name: string, inputs: ReadonlyArray<ParamType>) {
        super(guard, 'struct', name, inputs);
        Object.defineProperty(this, internal, { value: StructFragmentInternal });
    }

    /**
     *  Returns a string representation of this struct as %%format%%.
     */
    format(): string {
        throw new Error('@TODO');
    }

    /**
     *  Returns a new **StructFragment** for %%obj%%.
     */
    static from(obj: any): StructFragment {
        if (typeof obj === 'string') {
            return StructFragment.from(lex(obj));
        } else if (obj instanceof TokenString) {
            const name = consumeName('struct', obj);
            const inputs = consumeParams(obj);
            consumeEoi(obj);
            return new StructFragment(_guard, name, inputs);
        }

        return new StructFragment(_guard, obj.name, obj.inputs ? obj.inputs.map(ParamType.from) : []);
    }

    // @TODO: fix this return type
    /**
     *  Returns ``true`` and provides a type guard if %%value%% is a
     *  **StructFragment**.
     */
    static isFragment(value: any): value is FunctionFragment {
        return value && value[internal] === StructFragmentInternal;
    }
}