const Syntax = require('./syntax.js');
const Promise = require('any-promise');
const mapSeries = require('./util/promise.js').mapSeries;
const RenderBreakError = require('./util/error.js').RenderBreakError;
const RenderError = require('./util/error.js').RenderError;
const assert = require('./util/assert.js');

var render = {

    renderTemplates: function(templates, scope) {
        assert(scope, 'unable to evalTemplates: scope undefined');

        var html = '';
        return mapSeries(templates, (tpl) => {
            return renderTemplate.call(this, tpl)
                .then(partial => html += partial)
                .catch(e => {
                    if (e instanceof RenderBreakError) {
                        e.resolvedHTML = html;
                        throw e;
                    }
                    throw new RenderError(e, tpl);
                });
        }).then(() => html);

        function renderTemplate(template) {
            if (template.type === 'tag') {
                return this.renderTag(template, scope)
                    .then(partial => partial === undefined ? '' : partial);
            } else if (template.type === 'output') {
                return Promise.resolve()
                    .then(() => this.evalOutput(template, scope))
                    .then(partial => partial === undefined ? '' : stringify(partial));
            } else { // template.type === 'html'
                return Promise.resolve(template.value);
            }
        }
    },

    renderTag: function(template, scope) {
        if (template.name === 'continue') {
            return Promise.reject(new RenderBreakError('continue'));
        }
        if (template.name === 'break') {
            return Promise.reject(new RenderBreakError('break'));
        }
        return template.render(scope);
    },

    evalOutput: function(template, scope) {
        assert(scope, 'unable to evalOutput: scope undefined');
        return template.filters.reduce(
            (prev, filter) => filter.render(prev, scope),
            Syntax.evalExp(template.initial, scope));
    }
};

function factory() {
    var instance = Object.create(render);
    return instance;
}

function stringify(val) {
    if (typeof val === 'string') return val;
    return JSON.stringify(val);
}

module.exports = factory;