import { Translation } from "../UI/i18n/Translation"
import { DenominationConfigJson } from "./ThemeConfig/Json/UnitConfigJson"
import Translations from "../UI/i18n/Translations"
import { Store } from "../Logic/UIEventSource"
import BaseUIElement from "../UI/BaseUIElement"
import Toggle from "../UI/Input/Toggle"

export class Denomination {
    public readonly canonical: string
    public readonly _canonicalSingular: string
    public readonly useAsDefaultInput: boolean | string[]
    public readonly useIfNoUnitGiven: boolean | string[]
    public readonly prefix: boolean
    public readonly alternativeDenominations: string[]
    private readonly _human: Translation
    private readonly _humanSingular?: Translation

    constructor(json: DenominationConfigJson, context: string) {
        context = `${context}.unit(${json.canonicalDenomination})`
        this.canonical = json.canonicalDenomination.trim()
        if (this.canonical === undefined) {
            throw `${context}: this unit has no decent canonical value defined`
        }
        this._canonicalSingular = json.canonicalDenominationSingular?.trim()

        json.alternativeDenomination.forEach((v, i) => {
            if ((v?.trim() ?? "") === "") {
                throw `${context}.alternativeDenomination.${i}: invalid alternative denomination: undefined, null or only whitespace`
            }
        })

        this.alternativeDenominations = json.alternativeDenomination?.map((v) => v.trim()) ?? []

        if (json["default"] !== undefined) {
            throw `${context} uses the old 'default'-key. Use "useIfNoUnitGiven" or "useAsDefaultInput" instead`
        }
        this.useIfNoUnitGiven = json.useIfNoUnitGiven
        this.useAsDefaultInput = json.useAsDefaultInput ?? json.useIfNoUnitGiven

        this._human = Translations.T(json.human, context + "human")
        this._humanSingular = Translations.T(json.humanSingular, context + "humanSingular")

        this.prefix = json.prefix ?? false
    }

    get human(): Translation {
        return this._human.Clone()
    }

    get humanSingular(): Translation {
        return (this._humanSingular ?? this._human).Clone()
    }

    getToggledHuman(isSingular: Store<boolean>): BaseUIElement {
        if (this._humanSingular === undefined) {
            return this.human
        }
        return new Toggle(this.humanSingular, this.human, isSingular)
    }

    /**
     * Create a representation of the given value
     * @param value: the value from OSM
     * @param actAsDefault: if set and the value can be parsed as number, will be parsed and trimmed
     *
     * const unit = new Denomination({
     *               canonicalDenomination: "m",
     *               alternativeDenomination: ["meter"],
     *               human: {
     *                   en: "meter"
     *               }
     *           }, "test")
     * unit.canonicalValue("42m", true) // =>"42 m"
     * unit.canonicalValue("42", true) // =>"42 m"
     * unit.canonicalValue("42 m", true) // =>"42 m"
     * unit.canonicalValue("42 meter", true) // =>"42 m"
     * unit.canonicalValue("42m", true) // =>"42 m"
     * unit.canonicalValue("42", true) // =>"42 m"
     *
     * // Should be trimmed if canonical is empty
     * const unit = new Denomination({
     *               canonicalDenomination: "",
     *               alternativeDenomination: ["meter","m"],
     *               human: {
     *                   en: "meter"
     *               }
     *           }, "test")
     * unit.canonicalValue("42m", true) // =>"42"
     * unit.canonicalValue("42", true) // =>"42"
     * unit.canonicalValue("42 m", true) // =>"42"
     * unit.canonicalValue("42 meter", true) // =>"42"
     */
    public canonicalValue(value: string, actAsDefault: boolean): string {
        if (value === undefined) {
            return undefined
        }
        const stripped = this.StrippedValue(value, actAsDefault)
        if (stripped === null) {
            return null
        }
        if (stripped === "1" && this._canonicalSingular !== undefined) {
            return ("1 " + this._canonicalSingular).trim()
        }
        return (stripped + " " + this.canonical).trim()
    }

    /**
     * Returns the core value (without unit) if:
     * - the value ends with the canonical or an alternative value (or begins with if prefix is set)
     * - the value is a Number (without unit) and default is set
     *
     * Returns null if it doesn't match this unit
     */
    public StrippedValue(value: string, actAsDefault: boolean): string {
        if (value === undefined) {
            return undefined
        }

        value = value.toLowerCase()
        const self = this

        function startsWith(key) {
            if (self.prefix) {
                return value.startsWith(key)
            } else {
                return value.endsWith(key)
            }
        }

        function substr(key) {
            if (self.prefix) {
                return value.substr(key.length).trim()
            } else {
                return value.substring(0, value.length - key.length).trim()
            }
        }

        if (this.canonical !== "" && startsWith(this.canonical.toLowerCase())) {
            return substr(this.canonical)
        }

        if (
            this._canonicalSingular !== undefined &&
            this._canonicalSingular !== "" &&
            startsWith(this._canonicalSingular)
        ) {
            return substr(this._canonicalSingular)
        }

        for (const alternativeValue of this.alternativeDenominations) {
            if (startsWith(alternativeValue)) {
                return substr(alternativeValue)
            }
        }

        if (!actAsDefault) {
            return null
        }

        const parsed = Number(value.trim())
        if (!isNaN(parsed)) {
            return value.trim()
        }

        return null
    }

    isDefaultUnit(country: () => string) {
        if (this.useIfNoUnitGiven === true) {
            return true
        }
        if (this.useIfNoUnitGiven === false) {
            return false
        }
        return this.useIfNoUnitGiven.indexOf(country()) >= 0
    }
}