/**
 * @fileoverview Responsible for loading config files
 * @author Seth McLaughlin
 * @copyright 2014 Nicholas C. Zakas. All rights reserved.
 * @copyright 2013 Seth McLaughlin. All rights reserved.
 * @copyright 2014 Michael McLaughlin. All rights reserved.
 */
"use strict";

//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------

var fs = require("fs"),
    path = require("path"),
    environments = require("../conf/environments"),
    util = require("./util"),
    FileFinder = require("./file-finder"),
    stripComments = require("strip-json-comments"),
    assign = require("object-assign"),
    debug = require("debug"),
    yaml = require("js-yaml"),
    userHome = require("user-home"),
    isAbsolutePath = require("path-is-absolute"),
    validator = require("./config-validator");

//------------------------------------------------------------------------------
// Constants
//------------------------------------------------------------------------------

var LOCAL_CONFIG_FILENAME = ".eslintrc",
    PACKAGE_CONFIG_FILENAME = "package.json",
    PACKAGE_CONFIG_FIELD_NAME = "eslintConfig",
    PERSONAL_CONFIG_PATH = userHome ? path.join(userHome, LOCAL_CONFIG_FILENAME) : null;

//------------------------------------------------------------------------------
// Private
//------------------------------------------------------------------------------

var loadedPlugins = Object.create(null);

//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------

debug = debug("eslint:config");

/**
 * Determines if a given string represents a filepath or not using the same
 * conventions as require(), meaning that the first character must be nonalphanumeric
 * and not the @ sign which is used for scoped packages to be considered a file path.
 * @param {string} filePath The string to check.
 * @returns {boolean} True if it's a filepath, false if not.
 * @private
 */
function isFilePath(filePath) {
    return isAbsolutePath(filePath) || !/\w|@/.test(filePath[0]);
}

/**
 * Load and parse a JSON config object from a file.
 * @param {string} filePath the path to the JSON config file
 * @returns {Object} the parsed config object (empty object if there was a parse error)
 * @private
 */
function loadConfig(filePath) {
    var config = {};

    if (filePath) {

        if (isFilePath(filePath)) {
            try {
                config = yaml.safeLoad(stripComments(fs.readFileSync(filePath, "utf8"))) || {};
            } catch (e) {
                debug("Error reading YAML file: " + filePath);
                e.message = "Cannot read config file: " + filePath + "\nError: " + e.message;
                throw e;
            }

            if (path.basename(filePath) === PACKAGE_CONFIG_FILENAME) {
                config = config[PACKAGE_CONFIG_FIELD_NAME] || {};
            }

        } else {

            // it's a package
            if (filePath.indexOf("eslint-config-") === -1) {
                if (filePath.indexOf("@") === 0) {
                    // for scoped packages, insert the eslint-config after the first /
                    filePath = filePath.replace(/^([^\/]+\/)(.*)$/, "$1eslint-config-$2");
                } else {
                    filePath = "eslint-config-" + filePath;
                }
            }

            config = util.mergeConfigs(config, require(filePath));
        }

        validator.validate(config, filePath);

        // If an `extends` property is defined, it represents a configuration file to use as
        // a "parent". Load the referenced file and merge the configuration recursively.
        if (config.extends) {
            var configExtends = config.extends;

            if (!Array.isArray(config.extends)) {
                configExtends = [config.extends];
            }

            // Make the last element in an array take the highest precedence
            config = configExtends.reduceRight(function (previousValue, parentPath) {

                if (isFilePath(parentPath)) {
                    // If the `extends` path is relative, use the directory of the current configuration
                    // file as the reference point. Otherwise, use as-is.
                    parentPath = (!isAbsolutePath(parentPath) ?
                        path.join(path.dirname(filePath), parentPath) :
                        parentPath
                    );
                }

                try {
                    return util.mergeConfigs(loadConfig(parentPath), previousValue);
                } catch (e) {
                    // If the file referenced by `extends` failed to load, add the path to the
                    // configuration file that referenced it to the error message so the user is
                    // able to see where it was referenced from, then re-throw
                    e.message += "\nReferenced from: " + filePath;
                    throw e;
                }

            }, config);

        }


    }


    return config;
}

/**
 * Load configuration for all plugins provided.
 * @param {string[]} pluginNames An array of plugin names which should be loaded.
 * @returns {Object} all plugin configurations merged together
 */
function getPluginsConfig(pluginNames) {
    var pluginConfig = {};

    pluginNames.forEach(function (pluginName) {
        var pluginNamespace = util.getNamespace(pluginName),
            pluginNameWithoutNamespace = util.removeNameSpace(pluginName),
            pluginNameWithoutPrefix = util.removePluginPrefix(pluginNameWithoutNamespace),
            plugin = {},
            rules = {};

        if (!loadedPlugins[pluginNameWithoutPrefix]) {
            try {
                plugin = require(pluginNamespace + util.PLUGIN_NAME_PREFIX + pluginNameWithoutPrefix);
                loadedPlugins[pluginNameWithoutPrefix] = plugin;
            } catch(err) {
                debug("Failed to load plugin configuration for " + pluginNameWithoutPrefix + ". Proceeding without it.");
                plugin = { rulesConfig: {}};
            }
        } else {
            plugin = loadedPlugins[pluginNameWithoutPrefix];
        }

        if (!plugin.rulesConfig) {
            plugin.rulesConfig = {};
        }

        Object.keys(plugin.rulesConfig).forEach(function(item) {
            rules[pluginNameWithoutPrefix + "/" + item] = plugin.rulesConfig[item];
        });

        pluginConfig = util.mergeConfigs(pluginConfig, rules);
    });

    return {rules: pluginConfig};
}

/**
 * Get personal config object from ~/.eslintrc.
 * @returns {Object} the personal config object (empty object if there is no personal config)
 * @private
 */
function getPersonalConfig() {
    var config = {};

    if (PERSONAL_CONFIG_PATH && fs.existsSync(PERSONAL_CONFIG_PATH)) {
        debug("Using personal config");
        config = loadConfig(PERSONAL_CONFIG_PATH);
    }

    return config;
}

/**
 * Get a local config object.
 * @param {Object} thisConfig A Config object.
 * @param {string} directory The directory to start looking in for a local config file.
 * @returns {Object} The local config object, or an empty object if there is no local config.
 */
function getLocalConfig(thisConfig, directory) {
    var found,
        i,
        localConfig,
        localConfigFile,
        config = {},
        localConfigFiles = thisConfig.findLocalConfigFiles(directory),
        numFiles = localConfigFiles.length;

    for (i = 0; i < numFiles; i++) {

        localConfigFile = localConfigFiles[i];

        // Don't consider the personal config file in the home directory.
        if (localConfigFile === PERSONAL_CONFIG_PATH) {
            continue;
        }

        debug("Loading " + localConfigFile);
        localConfig = loadConfig(localConfigFile);

        // Don't consider a local config file found if the config is empty.
        if (!Object.keys(localConfig).length) {
            continue;
        }

        found = true;
        debug("Using " + localConfigFile);
        config = util.mergeConfigs(localConfig, config);
    }

    // Use the personal config file if there are no other local config files found.
    return found ? config : util.mergeConfigs(config, getPersonalConfig());
}

/**
 * Creates an environment config based on the specified environments.
 * @param {Object<string,boolean>} envs The environment settings.
 * @param {boolean} reset The value of the command line reset option. If true,
 *      rules are not automatically merged into the config.
 * @returns {Object} A configuration object with the appropriate rules and globals
 *      set.
 * @private
 */
function createEnvironmentConfig(envs, reset) {

    var envConfig = {
        globals: {},
        env: envs || {},
        rules: {},
        ecmaFeatures: {}
    };

    if (envs) {
        Object.keys(envs).filter(function (name) {
            return envs[name];
        }).forEach(function(name) {
            var environment = environments[name];

            if (environment) {

                if (!reset && environment.rules) {
                    assign(envConfig.rules, environment.rules);
                }

                if (environment.globals) {
                    assign(envConfig.globals, environment.globals);
                }

                if (environment.ecmaFeatures) {
                    assign(envConfig.ecmaFeatures, environment.ecmaFeatures);
                }
            }
        });
    }

    return envConfig;
}

//------------------------------------------------------------------------------
// API
//------------------------------------------------------------------------------

/**
 * Config
 * @constructor
 * @class Config
 * @param {Object} options Options to be passed in
 * @param {string} [cwd] current working directory. Defaults to process.cwd()
 */
function Config(options) {
    var useConfig;

    options = options || {};

    this.ignore = options.ignore;
    this.ignorePath = options.ignorePath;
    this.cache = {};

    if (options.reset || options.baseConfig === false) {
        // If `options.reset` is truthy or `options.baseConfig` is set to `false`,
        // disable all default rules and environments
        this.baseConfig = { rules: {} };
    } else {
        // If `options.baseConfig` is an object, just use it,
        // otherwise use default base config from `conf/eslint.json`
        this.baseConfig = options.baseConfig ||
                require(path.resolve(__dirname, "..", "conf", "eslint.json"));
    }

    this.useEslintrc = (options.useEslintrc !== false);

    this.env = (options.envs || []).reduce(function (envs, name) {
        envs[name] = true;
        return envs;
    }, {});

    this.globals = (options.globals || []).reduce(function (globals, def) {
        // Default "foo" to false and handle "foo:false" and "foo:true"
        var parts = def.split(":");
        globals[parts[0]] = (parts.length > 1 && parts[1] === "true");
        return globals;
    }, {});

    useConfig = options.configFile;
    this.options = options;

    if (useConfig) {
        debug("Using command line config " + useConfig);
        this.useSpecificConfig = loadConfig(path.resolve(process.cwd(), useConfig));
    }
}

/**
 * Build a config object merging the base config (conf/eslint.json), the
 * environments config (conf/environments.js) and eventually the user config.
 * @param {string} filePath a file in whose directory we start looking for a local config
 * @returns {Object} config object
 */
Config.prototype.getConfig = function (filePath) {
    var config,
        userConfig,
        directory = filePath ? path.dirname(filePath) : process.cwd(),
        pluginConfig;

    debug("Constructing config for " + (filePath ? filePath : "text"));

    config = this.cache[directory];

    if (config) {
        debug("Using config from cache");
        return config;
    }

    // Step 1: Determine user-specified config from .eslintrc and package.json files
    if (this.useEslintrc) {
        debug("Using .eslintrc and package.json files");
        userConfig = getLocalConfig(this, directory);
    } else {
        debug("Not using .eslintrc or package.json files");
        userConfig = {};
    }

    // Step 2: Create a copy of the baseConfig
    config = util.mergeConfigs({}, this.baseConfig);

    // Step 3: Merge in environment-specific globals and rules from .eslintrc files
    config = util.mergeConfigs(config, createEnvironmentConfig(userConfig.env, this.options.reset));

    // Step 4: Merge in the user-specified configuration from .eslintrc and package.json
    config = util.mergeConfigs(config, userConfig);

    // Step 5: Merge in command line config file
    if (this.useSpecificConfig) {
        debug("Merging command line config file");

        if (this.useSpecificConfig.env) {
            config = util.mergeConfigs(config, createEnvironmentConfig(this.useSpecificConfig.env, this.options.reset));
        }

        config = util.mergeConfigs(config, this.useSpecificConfig);
    }

    // Step 6: Merge in command line environments
    debug("Merging command line environment settings");
    config = util.mergeConfigs(config, createEnvironmentConfig(this.env, this.options.reset));

    // Step 7: Merge in command line rules
    if (this.options.rules) {
        debug("Merging command line rules");
        config = util.mergeConfigs(config, { rules: this.options.rules });
    }

    // Step 8: Merge in command line globals
    config = util.mergeConfigs(config, { globals: this.globals });


    // Step 9: Merge in plugin specific rules in reverse
    if (config.plugins) {
        pluginConfig = getPluginsConfig(config.plugins);
        config = util.mergeConfigs(pluginConfig, config);
    }

    this.cache[directory] = config;

    return config;
};

/**
 * Find local config files from directory and parent directories.
 * @param {string} directory The directory to start searching from.
 * @returns {string[]} The paths of local config files found.
 */
Config.prototype.findLocalConfigFiles = function (directory) {

    if (!this.localConfigFinder) {
        this.localConfigFinder = new FileFinder(LOCAL_CONFIG_FILENAME, PACKAGE_CONFIG_FILENAME);
    }

    return this.localConfigFinder.findAllInDirectoryAndParents(directory);
};

module.exports = Config;