'use strict';

const Assert = require('@hapi/hoek/lib/assert');
const Clone = require('@hapi/hoek/lib/clone');
const EscapeHtml = require('@hapi/hoek/lib/escapeHtml');
const Formula = require('@sideway/formula');

const Common = require('./common');
const Errors = require('./errors');
const Ref = require('./ref');


const internals = {
    symbol: Symbol('template'),

    opens: new Array(1000).join('\u0000'),
    closes: new Array(1000).join('\u0001'),

    dateFormat: {
        date: Date.prototype.toDateString,
        iso: Date.prototype.toISOString,
        string: Date.prototype.toString,
        time: Date.prototype.toTimeString,
        utc: Date.prototype.toUTCString
    }
};


module.exports = exports = internals.Template = class {

    constructor(source, options) {

        Assert(typeof source === 'string', 'Template source must be a string');
        Assert(!source.includes('\u0000') && !source.includes('\u0001'), 'Template source cannot contain reserved control characters');

        this.source = source;
        this.rendered = source;

        this._template = null;
        this._settings = Clone(options);

        this._parse();
    }

    _parse() {

        // 'text {raw} {{ref}} \\{{ignore}} {{ignore\\}} {{ignore {{ignore}'

        if (!this.source.includes('{')) {
            return;
        }

        // Encode escaped \\{{{{{

        const encoded = internals.encode(this.source);

        // Split on first { in each set

        const parts = internals.split(encoded);

        // Process parts

        let refs = false;
        const processed = [];
        const head = parts.shift();
        if (head) {
            processed.push(head);
        }

        for (const part of parts) {
            const raw = part[0] !== '{';
            const ender = raw ? '}' : '}}';
            const end = part.indexOf(ender);
            if (end === -1 ||                               // Ignore non-matching closing
                part[1] === '{') {                          // Ignore more than two {

                processed.push(`{${internals.decode(part)}`);
                continue;
            }

            let variable = part.slice(raw ? 0 : 1, end);
            const wrapped = variable[0] === ':';
            if (wrapped) {
                variable = variable.slice(1);
            }

            const dynamic = this._ref(internals.decode(variable), { raw, wrapped });
            processed.push(dynamic);
            if (typeof dynamic !== 'string') {
                refs = true;
            }

            const rest = part.slice(end + ender.length);
            if (rest) {
                processed.push(internals.decode(rest));
            }
        }

        if (!refs) {
            this.rendered = processed.join('');
            return;
        }

        this._template = processed;
    }

    static date(date, prefs) {

        return internals.dateFormat[prefs.dateFormat].call(date);
    }

    describe(options = {}) {

        if (!this._settings &&
            options.compact) {

            return this.source;
        }

        const desc = { template: this.source };
        if (this._settings) {
            desc.options = this._settings;
        }

        return desc;
    }

    static build(desc) {

        return new internals.Template(desc.template, desc.options);
    }

    isDynamic() {

        return !!this._template;
    }

    static isTemplate(template) {

        return template ? !!template[Common.symbols.template] : false;
    }

    refs() {

        if (!this._template) {
            return;
        }

        const refs = [];
        for (const part of this._template) {
            if (typeof part !== 'string') {
                refs.push(...part.refs);
            }
        }

        return refs;
    }

    resolve(value, state, prefs, local) {

        if (this._template &&
            this._template.length === 1) {

            return this._part(this._template[0], /* context -> [*/ value, state, prefs, local, {} /*] */);
        }

        return this.render(value, state, prefs, local);
    }

    _part(part, ...args) {

        if (part.ref) {
            return part.ref.resolve(...args);
        }

        return part.formula.evaluate(args);
    }

    render(value, state, prefs, local, options = {}) {

        if (!this.isDynamic()) {
            return this.rendered;
        }

        const parts = [];
        for (const part of this._template) {
            if (typeof part === 'string') {
                parts.push(part);
            }
            else {
                const rendered = this._part(part, /* context -> [*/ value, state, prefs, local, options /*] */);
                const string = internals.stringify(rendered, value, state, prefs, local, options);
                if (string !== undefined) {
                    const result = part.raw || (options.errors && options.errors.escapeHtml) === false ? string : EscapeHtml(string);
                    parts.push(internals.wrap(result, part.wrapped && prefs.errors.wrap.label));
                }
            }
        }

        return parts.join('');
    }

    _ref(content, { raw, wrapped }) {

        const refs = [];
        const reference = (variable) => {

            const ref = Ref.create(variable, this._settings);
            refs.push(ref);
            return (context) => ref.resolve(...context);
        };

        try {
            var formula = new Formula.Parser(content, { reference, functions: internals.functions, constants: internals.constants });
        }
        catch (err) {
            err.message = `Invalid template variable "${content}" fails due to: ${err.message}`;
            throw err;
        }

        if (formula.single) {
            if (formula.single.type === 'reference') {
                const ref = refs[0];
                return { ref, raw, refs, wrapped: wrapped || ref.type === 'local' && ref.key === 'label' };
            }

            return internals.stringify(formula.single.value);
        }

        return { formula, raw, refs };
    }

    toString() {

        return this.source;
    }
};


internals.Template.prototype[Common.symbols.template] = true;
internals.Template.prototype.isImmutable = true;                // Prevents Hoek from deep cloning schema objects


internals.encode = function (string) {

    return string
        .replace(/\\(\{+)/g, ($0, $1) => {

            return internals.opens.slice(0, $1.length);
        })
        .replace(/\\(\}+)/g, ($0, $1) => {

            return internals.closes.slice(0, $1.length);
        });
};


internals.decode = function (string) {

    return string
        .replace(/\u0000/g, '{')
        .replace(/\u0001/g, '}');
};


internals.split = function (string) {

    const parts = [];
    let current = '';

    for (let i = 0; i < string.length; ++i) {
        const char = string[i];

        if (char === '{') {
            let next = '';
            while (i + 1 < string.length &&
                string[i + 1] === '{') {

                next += '{';
                ++i;
            }

            parts.push(current);
            current = next;
        }
        else {
            current += char;
        }
    }

    parts.push(current);
    return parts;
};


internals.wrap = function (value, ends) {

    if (!ends) {
        return value;
    }

    if (ends.length === 1) {
        return `${ends}${value}${ends}`;
    }

    return `${ends[0]}${value}${ends[1]}`;
};


internals.stringify = function (value, original, state, prefs, local, options) {

    const type = typeof value;

    let skipWrap = false;
    if (Ref.isRef(value) &&
        value.render) {

        skipWrap = value.in;
        value = value.resolve(original, state, prefs, local, { in: value.in, ...options });
    }

    if (value === null) {
        return 'null';
    }

    if (type === 'string') {
        return value;
    }

    if (type === 'number' ||
        type === 'function' ||
        type === 'symbol') {

        return value.toString();
    }

    if (type !== 'object') {
        return JSON.stringify(value);
    }

    if (value instanceof Date) {
        return internals.Template.date(value, prefs);
    }

    if (value instanceof Map) {
        const pairs = [];
        for (const [key, sym] of value.entries()) {
            pairs.push(`${key.toString()} -> ${sym.toString()}`);
        }

        value = pairs;
    }

    if (!Array.isArray(value)) {
        return value.toString();
    }

    let partial = '';
    for (const item of value) {
        partial = partial + (partial.length ? ', ' : '') + internals.stringify(item, original, state, prefs, local, options);
    }

    if (skipWrap) {
        return partial;
    }

    return internals.wrap(partial, prefs.errors.wrap.array);
};


internals.constants = {

    true: true,
    false: false,
    null: null,

    second: 1000,
    minute: 60 * 1000,
    hour: 60 * 60 * 1000,
    day: 24 * 60 * 60 * 1000
};


internals.functions = {

    if(condition, then, otherwise) {

        return condition ? then : otherwise;
    },

    msg(code) {

        const [value, state, prefs, local, options] = this;
        const messages = options.messages;
        if (!messages) {
            return '';
        }

        const template = Errors.template(value, messages[0], code, state, prefs) || Errors.template(value, messages[1], code, state, prefs);
        if (!template) {
            return '';
        }

        return template.render(value, state, prefs, local, options);
    },

    number(value) {

        if (typeof value === 'number') {
            return value;
        }

        if (typeof value === 'string') {
            return parseFloat(value);
        }

        if (typeof value === 'boolean') {
            return value ? 1 : 0;
        }

        if (value instanceof Date) {
            return value.getTime();
        }

        return null;
    }
};