const escapeRegex = require('escape-string-regexp');
const moment = require('moment');

const { Argument, Observer } = require('../../../interfaces/');

const Constants = {
    QuotePairs: {
        '"': '"', //regular double
        "'": "'", //regular single
        "‘": "’", //smart single
        "“": "”" //smart double
    }
};

class CommandHandler extends Observer {

    constructor(client) {

        super(client, {
            name: 'commandHandler',
            priority: 5,
            guarded: true
        });

        this.client = client;

        this.hooks = [
            ['message', this.handleMessage.bind(this)]
        ];

        this._startQuotes = Object.keys(Constants.QuotePairs); //Used for the "getQuotes" function. Parses arguments with quotes in it to combine them into one array argument.
        this._quoteMarks = this._startQuotes + Object.values(Constants.QuotePairs) // ^
            .join('');

    }

    async handleMessage(message) {

        if(!this.client._built
            || message.webhookID
            || message.author.bot
            || message.guild && (!message.guild.available || message.guild.banned)) return undefined; 
        //Don't parse commands if client isn't built (commands aren't loaded), is a webhook, bot, or if the guild isn't available/is banned.

        if (message.guild) {
            if (!message.member) await message.guild.members.fetch(message.author.id); //Fetch member if discord.js doesn't fetch them automatically.
        }

        const { command, parameters } = await this._getCommand(message);
        if(!command) return undefined;
        message.command = command;
        
        // const timestamp1 = new Date().getTime();

        const response = await this._parseArguments(parameters, command.arguments, message.guild);
        if(response.error) {
            return this.handleError(message, { type: 'argument', ...response });
        }

        if(command.keepQuotes) {
            message.parameters = response.parameters.map(([param, isQuote]) => isQuote ? `"${param}"` : param);
        } else {
            message.parameters = response.parameters.map((p) => p[0]);
        }

        // const timestamp2 = new Date().getTime();
        // this.client.logger.debug(`Client took ${timestamp2-timestamp1}ms to parse arguments.`);

        message.arguments = response.args;
    
        return this.handleCommand(message, response.parameters);
        

    }

    async _parseArguments(parameters = [], args = [], guild = null) {

        parameters = this._getQuotes(parameters.join(' '));
        
        const { shortArgs, longArgs } = await this._createArguments(args);
        const regex = new RegExp(`([0-9]*)(${Object.keys(longArgs).sort((a, b) => b.length - a.length)
            .map((k) => escapeRegex(k))
            .join('|')})([0-9]*)`, 'iu');
    
        const findArgument = (word) => {
            const matches = regex.exec(word);
            const [one, two, ...chars] = word.split('');
            let arg = null, 
                value = null;
            if(one === '-' && two !== '-') {
                const name = [two, ...chars].join('');
                const shortFlag = shortArgs[name];
                if(shortFlag) {
                    arg = shortFlag;
                    arg._flag = true;
                }
            } else if(one === '-' && two === '-' || one === '—' && two !== '—') {
                const name = one === '—'
                    ? [two, ...chars].join('')
                    : chars.join('');
                const longFlag = longArgs[name];
                if(longFlag) {
                    arg = longFlag;
                    arg._flag = true;
                }
            } else if(matches && (matches[1] || matches[3])) {
                const [,, name] = matches;
                const number = matches[1] || matches[3];
                const argument = longArgs[name];
                if(argument && argument.types.includes('VERBAL')) {
                    arg = longArgs[name];
                    value = number;
                }
            } else if(longArgs[word.toLowerCase()]) {
                const argument = longArgs[word.toLowerCase()];
                if(argument && argument.types.includes('VERBAL')) {
                    arg = longArgs[word.toLowerCase()];
                }
            }
            return { arg, value };
        };


        const newParameters = [],
            newArguments = [];

        const lookBehind = async (argument) => { //Checks previous argument for an integer or float value, "15 points".
            let response = {};
            if(newParameters.length > 0 && ['INTEGER', 'FLOAT'].includes(argument.type)) {
                const [lastWord] = newParameters[newParameters.length-1];
                response = await this._parseArgumentType(argument, lastWord, guild);
                if(!response.error) {
                    newParameters.pop(); //Deletes latest parameter.
                    newArguments.push(argument); //Adds argument with value of the latest parameter.
                    return { error: false };
                } 
            }
            return { error: true, ...response };
        };

        const existing = (argument) => {
            let exists = false;
            for(const { name } of newArguments) {
                if(argument && argument.name === name) exists = true;
            }
            return exists;
        };

        let error = null,
            currentArgument = null;
            
        for(let i = 0; i < parameters.length; i++) {
            const [word, isQuote] = parameters[i];
            const { arg, value } = findArgument(word);
            if(currentArgument) { //One of the previous words had an argument, trying to parse the type until error.
                let response = await this._parseArgumentType(currentArgument, word, guild);
                if(response.error) {
                    if(response.force) { //Overrides error if min/max (stupid)
                        error = { argument: currentArgument, ...response };
                        break;
                    }
                    const behind = await lookBehind(currentArgument); //Check for "15 points" (lookbehind the argument)
                    if(!behind.error) {
                        if(!currentArgument.infinite) currentArgument = null;
                    } else {
                        if(currentArgument.required) {
                            if(currentArgument.empty) {
                                if(behind.force) response = behind; //Overrides error if min/max (stupid)
                                error = { argument: currentArgument, ...response };
                                break;
                            }
                        } else if(currentArgument.empty) {
                            currentArgument.setDefault();
                        }
                        newArguments.push(currentArgument);
                        currentArgument = null;
                    }
                    if(arg && !existing(arg)) { //TODO: Add a function for this repetitive code
                        if(value) { //Pre-matched value (15pts/pts15) found by regex, won't need a separate word to parse the argument.
                            const response = await this._parseArgumentType(arg, value, guild);
                            if(arg.required) {
                                if(response.error) {
                                    error = { argument: arg, ...response };
                                    break;
                                }
                            }
                            newArguments.push(arg);
                            if(arg.infinite) currentArgument = arg;
                        } else {
                            currentArgument = arg;
                        }
                    } else {
                        newParameters.push([word, isQuote]);
                    }
                } else {
                    newArguments.push(currentArgument);
                    if(!currentArgument.infinite) currentArgument = null;
                }
            } else if(arg && !existing(arg)) { //TODO: Add a function for this repetitive code //Trying to find a new argument to parse or add as a parameter.
                if(value) { //Pre-matched value (15pts/pts15) found by regex, won't need a separate word to parse the argument.
                    const response = await this._parseArgumentType(arg, value, guild);
                    if(arg.required) {
                        if(response.error) {
                            error = { argument: arg, ...response };
                            break;
                        }
                    }
                    newArguments.push(arg);
                    if(arg.infinite) currentArgument = arg;
                } else {
                    currentArgument = arg;
                }
            } else {
                newParameters.push([ word, isQuote ]);
            }
        }

        if(error) return error;

        if(currentArgument) { //Add the last argument awaiting to be parsed (argument was left hanging at the end w/o a value)
            const behind = await lookBehind(currentArgument);
            if(!behind.error) {
                newArguments.push(currentArgument);
            } else {
                if(currentArgument.empty) {
                    if(currentArgument.required) {
                        if(behind.force) return { argument: currentArgument, ...behind };
                        return {
                            index: 'COMMANDHANDLER_TYPE_ERROR',
                            argument: currentArgument,
                            error: true
                        };
                    }
                    currentArgument.setDefault();
                }
                newArguments.push(currentArgument);
            }
        }

        const object = {};
        newArguments.map((a) => object[a.name] = a); //eslint-disable-line no-return-assign

        return { parameters: newParameters, args: object, error: false };

    }

    async _parseArgumentType(argument, string, guild) { //Parsing argument values to make sure they're correct.
        
        const parse = async(argument, string, guild) => {
            
            let { error, value } = await this.parseType(argument.type, string, guild); //eslint-disable-line prefer-const
            if(error) {
                return {
                    index: 'COMMANDHANDLER_TYPE_ERROR',
                    error
                };
            }

            if(['INTEGER', 'FLOAT'].includes(argument.type)) {
                const { min, max } = argument;
                if(max !== null && value > max) {
                    if(!argument.ignoreInvalid) return {
                        index: `COMMANDHANDLER_NUMBERMAX_ERROR`,
                        args: { min, max },
                        force: true,
                        error: true
                    };
                    value = argument.max;
                } else if(min !== null && value < min) {
                    if(!argument.ignoreInvalid) return {
                        index: `COMMANDHANDLER_NUMBERMIN_ERROR`,
                        args: { min, max },
                        force: true,
                        error: true
                    };
                    value = argument.min;
                }
            }

            if(argument.options.length > 0 && !argument.options.includes(value)) return {
                index: `COMMANDHANDLER_OPTIONS_ERROR`,
                args: { options: argument.options.map((o) => `\`${o}\``).join(', ') },
                error: true
            };

            return { error: false, value };

        };

        const response = await parse(argument, string, guild);

        if(response.error) {
            return response;
        }

        const { value } = response;
        if(value) {
            if(argument.infinite) argument.value.push(value);
            else argument.value = value;
        } else {
            argument.setDefault(guild);
        }

        return response;
    
    }

    async _createArguments(args) {

        const shortArgs = {}, 
            longArgs = {};

        let argKeys = [];
        for(let arg of args) {
            arg = new Argument(this.client, arg);

            const letters = [];
            const names = [ arg.name, ...arg.aliases ];
            argKeys = [...argKeys, ...names];

            for(const name of names) {
                longArgs[name] = arg;

                if(!arg.types.includes('FLAG')) continue;

                let letter = name.slice(0, 1);
                if(letters.includes(letter)) continue;
                if(argKeys.includes(letter)) letter = letter.toUpperCase();
                if(argKeys.includes(letter)) {
                    // this.client.logger.warn(`Command has too many arguments with the same first letter: ${argKeys.join(', ')}`);
                    break;
                }

                argKeys.push(letter);
                letters.push(letter);

                shortArgs[letter] = arg;
            }
    
        }

        return { shortArgs, longArgs };

    }

    async _getCommand(message) {

        const [ arg1, arg2, ...args ] = message.content.split(' ');

        if(message.guild) await message.guild.settings();
        const { prefix } = message;

        let command = null, 
            remains = [];
        if(arg1 && arg1.startsWith(prefix)) {
            const commandName = arg1.slice(prefix.length); //Grabs the command name by slicing off the prefix.
            command = await this._matchCommand(message, commandName);
            remains = [arg2, ...args];
        } else if(arg1 && arg2 && arg1.startsWith('<@')) { //Checks if the first argument is a mention and if a command is after it.
            const pattern = new RegExp(`^(<@!?${this.client.user.id}>)`, 'iu');
            if(arg2 && pattern.test(arg1)) {
                command = await this._matchCommand(message, arg2);
            }
            remains = args;
        }

        return { command, parameters: remains };

    }


    async _matchCommand(message, commandName) {

        const [ command ] = this.client.resolver.components(commandName, 'command', true);
        if(!command) return null;
        
        //Eventually search for custom commands here.

        message._caller = commandName; //Used for hidden commands as aliases.
        return command;

    }

    /* Command Handling */

    async handleCommand(message) {
        
        const inhibitors = await this._handleInhibitors(message);

        const silent = inhibitors.filter((i) => i.inhibitor.silent);
        const nonsilent = inhibitors.filter((i) => !i.inhibitor.silent);

        if(nonsilent.length === 0 && silent.length > 0) return undefined;
        if(nonsilent.length > 0) return this.handleError(message, { type: 'inhibitor', ...nonsilent[0] });

        const resolved = await message.resolve();
        if(resolved.error) {
            this.client.logger.error(`Command Error | ${message.command.resolveable} | Message ID: ${message.id}\n${resolved.message.stack || resolved.message}`);
            if(resolved.message.code === 50013) {
                const missing = message.channel.permissionsFor(message.guild.me).missing(['EMBED_LINKS']);
                if(missing.length > 0) {
                    return message.respond(message.format('COMMANDHANDLER_COMMAND_MISSINGPERMISSIONS'), {
                        emoji: 'failure'
                    });
                }
            }
            return this.handleError(message, { type: 'command' });
        }

        return true;

    }

    async _handleInhibitors(message) {

        const inhibitors = this.client.registry.components.filter((c) => c.type === 'inhibitor' && !c.disabled);
        if(inhibitors.size === 0) return [];

        const promises = [];
        for(const inhibitor of inhibitors.values()) { // Loops through all inhibitors, executing them.
            if(inhibitor.guild && !message.guild) continue;
            promises.push((async () => {
                let inhibited = inhibitor.execute(message, message.command);
                if(inhibited instanceof Promise) inhibited = await inhibited;
                return inhibited;
            })());
        }

        const reasons = (await Promise.all(promises)).filter((p) => p.error); // Filters out inhibitors with only errors.
        if(reasons.length === 0) return [];
        
        reasons.sort((a, b) => b.inhibitor.priority - a.inhibitor.priority); // Sorts inhibitor errors by most important.
        return reasons;

    }


    async parseType(type, str, guild) { //Types used for parsing argument types.

        const types = {
            STRING: (str) => ({ error: false, value: str }),
            INTEGER: (str) => {
                const int = parseInt(str);
                if(Math.round(int) !== int) return { error: true };
                if(isNaN(int)) return { error: true };
                return { error: false, value: int };
            },
            FLOAT: (str) => {
                const float = parseInt(str);
                if(isNaN(float)) return { error: true };
                return { error: false, value: float };
            },
            BOOLEAN: (str) => {
                const bool = this.client.resolver.resolveBoolean(str);
                if(bool === null) return { error: true };
                return { error: false, value: bool };
            },
            USER: async (str) => {
                const user = await this.client.resolver.resolveUser(str, true);
                if(!user) return { error: true };
                return { error: false, value: user };
            },
            MEMBER: async (str, guild) => {
                const member = await this.client.resolver.resolveMember(str, true, guild);
                if(!member) return { error: true };
                return { error: false, value: member };
            },
            TEXTCHANNEL: async (str, guild) => {
                const channel = await this.client.resolver.resolveChannel(str, true, guild, (channel) => channel.type === 'text');
                if(!channel) return { error: true };
                return { error: false, value: channel };
            },
            VOICECHANNEL: async(str, guild) => {
                const channel = await this.client.resolver.resolveChannel(str, true, guild, (channel) => channel.type === 'voice');
                if(!channel) return { error: true };
                return { error: false, value: channel };
            },
            CHANNEL: async (str, guild) => {
                const channel = await this.client.resolver.resolveChannel(str, true, guild);
                if(!channel) return { error: true };
                return { error: false, value: channel };
            },
            ROLE: async (str, guild) => {
                const role = await this.client.resolver.resolveRole(str, true, guild);
                if(!role) return { error: true };
                return { error: false, value: role };
            },
            TIME: async(str) => {
                const time = await this.client.resolver.resolveTime(str);
                if(!time) return { error: true };
                return { error: false, value: time }; 
            },
            DATE: async(str) => {
                const date = await this.client.resolver.resolveDate(str);
                if(!date) return { error: true };
                return { error: false, value: date };
            }
        };
        
        return types[type](str, guild);
    }


    /* Made by my friend Qwerasd#5202 */
    // I'm not entirely sure how this works, except for the fact that it loops through each CHARACTER and tries to match quotes together.
    // Supposedly quicker than regex, and I'd agree with that statement. Big, messy, but quick. Also lets you know if the grouped word(s) was a quote or not, which is useful for non-spaced quotes e.g. "Test" vs. "Test Test"
    _getQuotes(string) {
        if(!string) return [];

        let quoted = false,
            wordStart = true,
            startQuote = '',
            endQuote = false,
            isQuote = false,
            word = '';

        const words = [],
            chars = string.split('');

        chars.forEach((char) => {
            if((/\s/u).test(char)) {
                if(endQuote) {
                    quoted = false;
                    endQuote = false;
                    isQuote = true;
                }
                if(quoted) {
                    word += char;
                } else if(word !== '') {
                    words.push([ word, isQuote ]);
                    isQuote = false;
                    startQuote = '';
                    word = '';
                    wordStart = true;
                }
            } else if(this._quoteMarks.includes(char)) {
                if (endQuote) {
                    word += endQuote;
                    endQuote = false;
                }
                if(quoted) {
                    if(char === Constants.QuotePairs[startQuote]) {
                        endQuote = char;
                    } else {
                        word += char;
                    }
                } else if(wordStart && this._startQuotes.includes(char)) {
                    quoted = true;
                    startQuote = char;
                } else {
                    word += char;
                }
            } else {
                if(endQuote) {
                    word += endQuote;
                    endQuote = false;
                }
                word += char;
                wordStart = false;
            }
        });

        if (endQuote) {
            words.push([ word, true ]);
        } else {
            word.split(/\s/u).forEach((subWord, i) => {
                if (i === 0) {
                    words.push([ startQuote+subWord, false ]);
                } else {
                    words.push([ subWord, false ]);
                }
            });
        }

        return words;

    }

    async handleError(message, error) { //Handle different types of errors
        
        const messages = {
            command: async () => message.format('COMMANDHANDLER_COMMAND_ERROR', {
                invite: this.client._options.bot.invite, 
                id: message.id, 
                command: message.command.moduleResolveable,
                date: moment().format('YYYY-MM-DD')
            }),
            inhibitor: ({ inhibitor, args }) => `${message.format(inhibitor.index, { command: message.command.moduleResolveable, ...args })} **\`[${inhibitor.resolveable}]\`**`,
            argument: ({ index, args, argument }) => {
                const type = message.format('COMMANDHANDLER_TYPES', { type: argument.type }, true);
                return message.format(index, { type, arg: `${message.command.name}:${argument.name}`, ...args });
            }
        };

        //return this.client.rateLimiter.limitSend(message.channel, await messages[error.type](error));
        return message.limitedRespond(await messages[error.type](error), { emoji: 'failure', limit: 10, utility: error.type });

    }

}

module.exports = CommandHandler;