const _ = require('./util/underscore.js');
const lexical = require('./lexical.js');
const assert = require('./util/assert.js');
const toStr = Object.prototype.toString;

var Scope = {
    getAll: function() {
        var ctx = {};
        for (var i = this.scopes.length - 1; i >= 0; i--) {
            _.assign(ctx, this.scopes[i]);
        }
        return ctx;
    },
    get: function(str) {
        for (var i = this.scopes.length - 1; i >= 0; i--) {
            try {
                return this.getPropertyByPath(this.scopes[i], str);
            } catch (e) {
                if (/undefined variable/.test(e.message)) {
                    continue;
                }
                if (/Cannot read property/.test(e.message)) {
                    if (this.opts.strict_variables) {
                        e.message += ': ' + str;
                        throw e;
                    } else {
                        continue;
                    }
                } else {
                    e.message += ': ' + str;
                    throw e;
                }
            }
        }
        if (this.opts.strict_variables) {
            throw new TypeError('undefined variable: ' + str);
        }
    },
    set: function(k, v) {
        this.setPropertyByPath(this.scopes[this.scopes.length - 1], k, v);
        return this;
    },
    push: function(ctx) {
        assert(ctx, `trying to push ${ctx} into scopes`);
        return this.scopes.push(ctx);
    },
    pop: function() {
        return this.scopes.pop();
    },
    unshift: function(ctx) {
        assert(ctx, `trying to push ${ctx} into scopes`);
        return this.scopes.unshift(ctx);
    },
    shift: function() {
        return this.scopes.shift();
    },
    setPropertyByPath: function(obj, path, val) {
        if (_.isString(path)) {
            var paths = path.replace(/\[/g, '.').replace(/\]/g, '').split('.');
            for (var i = 0; i < paths.length; i++) {
                var key = paths[i];
                if (i === paths.length - 1) {
                    return obj[key] = val;
                }
                if (undefined === obj[key]) obj[key] = {};
                // case for readonly objects
                obj = obj[key] || {};
            }
        }
    },

    getPropertyByPath: function(obj, path) {
        var paths = this.propertyAccessSeq(path + '');
        var varName = paths.shift();
        if (!obj.hasOwnProperty(varName)) {
            throw new TypeError('undefined variable');
        }
        var variable = obj[varName];
        var lastName = paths.pop();
        paths.forEach(p => variable = variable[p]);
        if (undefined !== lastName) {
            if (lastName === 'size' && 
                (toStr.call(variable) === '[object Array]' 
                    || toStr.call(variable) === '[object String]')) {
                return variable.length;
            }
            variable = variable[lastName]
        }
        return variable;
    },

    /*
     * Parse property access sequence from access string
     * @example
     * accessSeq("foo.bar")            // ['foo', 'bar']
     * accessSeq("foo['bar']")      // ['foo', 'bar']
     * accessSeq("foo['b]r']")      // ['foo', 'b]r']
     * accessSeq("foo[bar.coo]")    // ['foo', 'bar'], for bar.coo == 'bar'
     */
    propertyAccessSeq: function(str) {
        var seq = [],
            name = '';
        for (var i = 0; i < str.length; i++) {
            if (str[i] === '[') {
                seq.push(name);
                name = '';

                var delemiter = str[i + 1];
                // foo[bar.coo]
                if (delemiter !== "'" && delemiter !== '"') {
                    var j = matchRightBracket(str, i + 1);
                    assert(j !== -1, `unbalanced []: ${str}`);
                    name = str.slice(i + 1, j);
                    // foo[1]
                    if (lexical.isInteger(name)) {
                        seq.push(name);
                    }
                    // foo["bar"]
                    else {
                        seq.push(this.get(name));
                    }
                    name = '';
                    i = j;
                }
                // foo["bar"]
                else {
                    j = str.indexOf(delemiter, i + 2);
                    assert(j !== -1, `unbalanced ${delemiter}: ${str}`);
                    name = str.slice(i + 2, j);
                    seq.push(name);
                    name = '';
                    i = j + 1;
                }
            }
            // foo.bar
            else if (str[i] === ".") {
                seq.push(name);
                name = '';
            }
            //foo.bar
            else {
                name += str[i];
            }
        }
        if (name.length) seq.push(name);
        return seq;
    }
};

function matchRightBracket(str, begin) {
    var stack = 1; // count of '[' - count of ']'
    for (var i = begin; i < str.length; i++) {
        if (str[i] === '[') {
            stack++;
        }
        if (str[i] === ']') {
            stack--;
            if (stack === 0) {
                return i;
            }
        }
    }
    return -1;
}

exports.factory = function(ctx, opts) {
    opts = _.assign({
        strict_variables: false,
        strict_filters: false,
        blocks: {},
        root: []
    }, opts);

    ctx = _.assign(ctx, {
        liquid: opts
    });

    var scope = Object.create(Scope);
    scope.opts = opts;
    scope.scopes = [ctx];
    return scope;
};