/* jslint node: true */
'use strict';

//  ENiGMA½
const loadMenu  = require('./menu_util.js').loadMenu;
const Errors    = require('./enig_error.js').Errors;

//  deps
const _         = require('lodash');
const assert    = require('assert');

//  :TODO: Stack is backwards.... top should be most recent! :)

module.exports = class MenuStack {
    constructor(client) {
        this.client = client;
        this.stack  = [];
    }

    push(moduleInfo) {
        return this.stack.push(moduleInfo);
    }

    pop() {
        return this.stack.pop();
    }

    peekPrev() {
        if(this.stackSize > 1) {
            return this.stack[this.stack.length - 2];
        }
    }

    top() {
        if(this.stackSize > 0) {
            return this.stack[this.stack.length - 1];
        }
    }

    get stackSize() {
        return this.stack.length;
    }

    get currentModule() {
        const top = this.top();
        if(top) {
            return top.instance;
        }
    }

    next(cb) {
        const currentModuleInfo = this.top();
        assert(currentModuleInfo, 'Empty menu stack!');

        const menuConfig    = currentModuleInfo.instance.menuConfig;
        const nextMenu      = this.client.acs.getConditionalValue(menuConfig.next, 'next');
        if(!nextMenu) {
            return cb(Array.isArray(menuConfig.next) ?
                Errors.MenuStack('No matching condition for "next"', 'NOCONDMATCH') :
                Errors.MenuStack('Invalid or missing "next" member in menu config', 'BADNEXT')
            );
        }

        if(nextMenu === currentModuleInfo.name) {
            return cb(Errors.MenuStack('Menu config "next" specifies current menu', 'ALREADYTHERE'));
        }

        this.goto(nextMenu, { }, cb);
    }

    prev(cb) {
        const menuResult = this.top().instance.getMenuResult();

        //  :TODO: leave() should really take a cb...
        this.pop().instance.leave();    //  leave & remove current

        const previousModuleInfo = this.pop();  //  get previous

        if(previousModuleInfo) {
            const opts = {
                extraArgs       : previousModuleInfo.extraArgs,
                savedState      : previousModuleInfo.savedState,
                lastMenuResult  : menuResult,
            };

            return this.goto(previousModuleInfo.name, opts, cb);
        }

        return cb(Errors.MenuStack('No previous menu available', 'NOPREV'));
    }

    goto(name, options, cb) {
        const currentModuleInfo = this.top();

        if(!cb && _.isFunction(options)) {
            cb = options;
            options = {};
        }

        options = options || {};
        const self = this;

        if(currentModuleInfo && name === currentModuleInfo.name) {
            if(cb) {
                cb(Errors.MenuStack('Already at supplied menu', 'ALREADYTHERE'));
            }
            return;
        }

        const loadOpts = {
            name        : name,
            client      : self.client,
        };

        if(currentModuleInfo && currentModuleInfo.menuFlags.includes('forwardArgs')) {
            loadOpts.extraArgs = currentModuleInfo.extraArgs;
        } else {
            loadOpts.extraArgs = options.extraArgs || _.get(options, 'formData.value');
        }
        loadOpts.lastMenuResult = options.lastMenuResult;

        loadMenu(loadOpts, (err, modInst) => {
            if(err) {
                //  :TODO: probably should just require a cb...
                const errCb = cb || self.client.defaultHandlerMissingMod();
                errCb(err);
            } else {
                self.client.log.debug( { menuName : name }, 'Goto menu module');

                //
                //  If menuFlags were supplied in menu.hjson, they should win over
                //  anything supplied in code.
                //
                let menuFlags;
                if(0 === modInst.menuConfig.options.menuFlags.length) {
                    menuFlags = Array.isArray(options.menuFlags) ? options.menuFlags : [];
                } else {
                    menuFlags = modInst.menuConfig.options.menuFlags;

                    //  in code we can ask to merge in
                    if(Array.isArray(options.menuFlags) && options.menuFlags.includes('mergeFlags')) {
                        menuFlags = _.uniq(menuFlags.concat(options.menuFlags));
                    }
                }

                if(currentModuleInfo) {
                    //  save stack state
                    currentModuleInfo.savedState = currentModuleInfo.instance.getSaveState();

                    currentModuleInfo.instance.leave();

                    if(currentModuleInfo.menuFlags.includes('noHistory')) {
                        this.pop();
                    }

                    if(menuFlags.includes('popParent')) {
                        this.pop().instance.leave();    //  leave & remove current
                    }
                }

                self.push({
                    name        : name,
                    instance    : modInst,
                    extraArgs   : loadOpts.extraArgs,
                    menuFlags   : menuFlags,
                });

                //  restore previous state if requested
                if(options.savedState) {
                    modInst.restoreSavedState(options.savedState);
                }

                const stackEntries = self.stack.map(stackEntry => {
                    let name = stackEntry.name;
                    if(stackEntry.instance.menuConfig.options.menuFlags.length > 0) {
                        name += ` (${stackEntry.instance.menuConfig.options.menuFlags.join(', ')})`;
                    }
                    return name;
                });

                self.client.log.trace( { stack : stackEntries }, 'Updated menu stack' );

                modInst.enter();

                if(cb) {
                    cb(null);
                }
            }
        });
    }
};