import {ValidationResult, ValidatorFunction} from './types'

/** Requires the input value to be an array. */
function is(fieldName: string, inputValue: unknown): ValidationResult {
    if ( Array.isArray(inputValue) ) {
        return { valid: true }
    }

    return {
        valid: false,
        message: 'must be an array',
    }
}

/** Requires the values in the input value array to be distinct. */
function distinct(fieldName: string, inputValue: unknown): ValidationResult {
    const arr = is(fieldName, inputValue)
    if ( !arr.valid ) {
        return arr
    }

    if ( Array.isArray(inputValue) && (new Set(inputValue)).size === inputValue.length ) {
        return { valid: true }
    }

    return {
        valid: false,
        message: 'must not contain duplicate values',
    }
}

/**
 * Builds a validator function that requires the input array to contain the given value.
 * @param value
 */
function includes(value: unknown): ValidatorFunction {
    return (fieldName: string, inputValue: unknown): ValidationResult => {
        const arr = is(fieldName, inputValue)
        if ( !arr.valid ) {
            return arr
        }

        if ( Array.isArray(inputValue) && inputValue.includes(value) ) {
            return { valid: true }
        }

        return {
            valid: false,
            message: `must include ${value}`,
        }
    }
}

/**
 * Builds a validator function that requires the input array NOT to contain the given value.
 * @param value
 */
function excludes(value: unknown): ValidatorFunction {
    return (fieldName: string, inputValue: unknown): ValidationResult => {
        const arr = is(fieldName, inputValue)
        if ( !arr.valid ) {
            return arr
        }

        if ( Array.isArray(inputValue) && !inputValue.includes(value) ) {
            return { valid: true }
        }

        return {
            valid: false,
            message: `must not include ${value}`,
        }
    }
}

/**
 * Builds a validator function that requires the input array to have exactly `len` many entries.
 * @param len
 */
function length(len: number): ValidatorFunction {
    return (fieldName: string, inputValue: unknown): ValidationResult => {
        const arr = is(fieldName, inputValue)
        if ( !arr.valid ) {
            return arr
        }

        if ( Array.isArray(inputValue) && inputValue.length === len ) {
            return { valid: true }
        }

        return {
            valid: false,
            message: `must be exactly of length ${len}`,
        }
    }
}

/**
 * Builds a validator function that requires the input array to have at least `len` many entries.
 * @param len
 */
function lengthMin(len: number): ValidatorFunction {
    return (fieldName: string, inputValue: unknown): ValidationResult => {
        const arr = is(fieldName, inputValue)
        if ( !arr.valid ) {
            return arr
        }

        if ( Array.isArray(inputValue) && inputValue.length >= len ) {
            return { valid: true }
        }

        return {
            valid: false,
            message: `must be at least length ${len}`,
        }
    }
}

/**
 * Builds a validator function that requires the input array to have at most `len` many entries.
 * @param len
 */
function lengthMax(len: number): ValidatorFunction {
    return (fieldName: string, inputValue: unknown): ValidationResult => {
        const arr = is(fieldName, inputValue)
        if ( !arr.valid ) {
            return arr
        }

        if ( Array.isArray(inputValue) && inputValue.length <= len ) {
            return { valid: true }
        }

        return {
            valid: false,
            message: `must be at most length ${len}`,
        }
    }
}

export const Arr = {
    is,
    distinct,
    includes,
    excludes,
    length,
    lengthMin,
    lengthMax,
}