'use strict';

var crypto = require('crypto');
var debug = require('debug')('windshaft:templates');
var _ = require('underscore');
var dot = require('dot');

var EventEmitter = require('events').EventEmitter;
var util = require('util');

// Class handling map templates
//
// See http://github.com/CartoDB/Windshaft-cartodb/wiki/Template-maps
//
// @param redis_pool an instance of a "redis-mpool"
//        See https://github.com/CartoDB/node-redis-mpool
//        Needs version 0.x.x of the API.
//
// @param opts TemplateMap options. Supported elements:
//    'max_user_templates' limit on the number of per-user
//
//
function TemplateMaps (redis_pool, opts) {
    if (!(this instanceof TemplateMaps)) {
        return new TemplateMaps();
    }

    EventEmitter.call(this);

    this.redis_pool = redis_pool;
    this.opts = opts || {};

    // Database containing templates
    // TODO: allow configuring ?
    // NOTE: currently it is the same as
    //       the one containing layergroups
    this.db_signatures = 0;

    //
    // Map templates are owned by a user that specifies access permissions
    // for their instances.
    //
    // We have the following datastores:
    //
    //  1. User templates: set of per-user map templates

    // User templates (HASH:tpl_id->tpl_val)
    this.key_usr_tpl = dot.template('map_tpl|{{=it.owner}}');
}

util.inherits(TemplateMaps, EventEmitter);

module.exports = TemplateMaps;

// --------------- PRIVATE METHODS --------------------------------

TemplateMaps.prototype._userTemplateLimit = function () {
    return this.opts.max_user_templates || 0;
};

/**
 * Internal function to communicate with redis
 *
 * @param redisFunc - the redis function to execute
 * @param redisArgs - the arguments for the redis function in an array
 * @param callback - function to pass results too.
 */
TemplateMaps.prototype._redisCmd = function (redisFunc, redisArgs, callback) {
    this.redis_pool.acquire(this.db_signatures, (err, redisClient) => {
        if (err) {
            return callback(err);
        }

        redisClient[redisFunc.toUpperCase()](...redisArgs, (err, data) => {
            this.redis_pool.release(this.db_signatures, redisClient);
            if (err) {
                return callback(err);
            }
            return callback(null, data);
        });
    });
};

var _reValidNameIdentifier = /^[a-z0-9][0-9a-z_\-]*$/i;
var _reValidPlaceholderIdentifier = /^[a-z][0-9a-z_]*$/i;
// jshint maxcomplexity:15
TemplateMaps.prototype._checkInvalidTemplate = function (template) {
    if (template.version !== '0.0.1') {
        return new Error('Unsupported template version ' + template.version);
    }
    var tplname = template.name;
    if (!tplname) {
        return new Error('Missing template name');
    }
    if (!tplname.match(_reValidNameIdentifier)) {
        return new Error("Invalid characters in template name '" + tplname + "'");
    }

    var invalidError = isInvalidLayergroup(template.layergroup);
    if (invalidError) {
        return invalidError;
    }

    var placeholders = template.placeholders || {};

    var placeholderKeys = Object.keys(placeholders);
    for (var i = 0, len = placeholderKeys.length; i < len; i++) {
        var placeholderKey = placeholderKeys[i];

        if (!placeholderKey.match(_reValidPlaceholderIdentifier)) {
            return new Error("Invalid characters in placeholder name '" + placeholderKey + "'");
        }
        if (!placeholders[placeholderKey].hasOwnProperty('default')) {
            return new Error("Missing default for placeholder '" + placeholderKey + "'");
        }
        if (!placeholders[placeholderKey].hasOwnProperty('type')) {
            return new Error("Missing type for placeholder '" + placeholderKey + "'");
        }
    }

    var auth = template.auth || {};

    switch (auth.method) {
    case 'open':
        break;
    case 'token':
        if (!_.isArray(auth.valid_tokens)) {
            return new Error("Invalid 'token' authentication: missing valid_tokens");
        }
        if (!auth.valid_tokens.length) {
            return new Error("Invalid 'token' authentication: no valid_tokens");
        }
        break;
    default:
        return new Error('Unsupported authentication method: ' + auth.method);
    }

    return false;
};

function isInvalidLayergroup (layergroup) {
    if (!layergroup) {
        return new Error('Missing layergroup');
    }

    var layers = layergroup.layers;

    if (!_.isArray(layers) || layers.length === 0) {
        return new Error('Missing or empty layers array from layergroup config');
    }

    var invalidLayers = layers
        .map(function (layer, layerIndex) {
            return layer.options ? null : layerIndex;
        })
        .filter(function (layerIndex) {
            return layerIndex !== null;
        });

    if (invalidLayers.length) {
        return new Error('Missing `options` in layergroup config for layers: ' + invalidLayers.join(', '));
    }

    return false;
}

function templateDefaults (template) {
    var templateAuth = _.defaults({}, template.auth || {}, {
        method: 'open'
    });
    return _.defaults({ auth: templateAuth }, template, {
        placeholders: {}
    });
}

/**
 * Checks if the if the user reaches the templetes limit
 *
 * @param userTemplatesKey user templat key in Redis
 * @param owner cartodb username of the template owner
 * @param callback returns error if the user reaches the limit
 */
TemplateMaps.prototype._checkUserTemplatesLimit = function (userTemplatesKey, owner, callback) {
    const limit = this._userTemplateLimit();

    if (!limit) {
        return callback();
    }

    this._redisCmd('HLEN', [userTemplatesKey], (err, numberOfTemplates) => {
        if (err) {
            return callback(err);
        }

        if (numberOfTemplates >= limit) {
            const limitReachedError = new Error(
                `User '${owner}' reached limit on number of templates (${numberOfTemplates}/${limit})`
            );
            limitReachedError.http_status = 409;
            return callback(limitReachedError);
        }

        return callback();
    });
};

// --------------- PUBLIC API -------------------------------------

// Add a template
//
// NOTE: locks user+template_name or fails
//
// @param owner cartodb username of the template owner
//
// @param template layergroup template, see
//        http://github.com/CartoDB/Windshaft-cartodb/wiki/Template-maps#template-format
//
// @param callback function(err, tpl_id)
//        Return template identifier (only valid for given user)
//
TemplateMaps.prototype.addTemplate = function (owner, template, callback) {
    template = templateDefaults(template);

    var invalidError = this._checkInvalidTemplate(template);
    if (invalidError) {
        return callback(invalidError);
    }

    var userTemplatesKey = this.key_usr_tpl({ owner });

    this._checkUserTemplatesLimit(userTemplatesKey, owner, err => {
        if (err) {
            return callback(err);
        }

        let templateString;
        try {
            templateString = JSON.stringify(template);
        } catch (error) {
            return callback(error);
        }

        this._redisCmd('HSETNX', [userTemplatesKey, template.name, templateString], (err, wasSet) => {
            if (err) {
                return callback(err);
            }

            if (!wasSet) {
                var templateExistsError = new Error(`Template '${template.name}' of user '${owner}' already exists`);
                return callback(templateExistsError);
            }

            this.emit('add', owner, template.name, template);
            return callback(null, template.name, template);
        });
    });
};

// Delete a template
//
// @param owner cartodb username of the template owner
//
// @param tpl_id template identifier as returned
//        by addTemplate or listTemplates
//
// @param callback function(err)
//
TemplateMaps.prototype.delTemplate = function (owner, tpl_id, callback) {
    this._redisCmd('HDEL', [this.key_usr_tpl({ owner: owner }), tpl_id], (err, deleted) => {
        if (err) {
            return callback(err);
        }

        if (!deleted) {
            return callback(new Error(`Template '${tpl_id}' of user '${owner}' does not exist`));
        }

        this.emit('delete', owner, tpl_id);
        return callback();
    });
};

// Update a template
//
// NOTE: locks user+template_name or fails
//
// Also deletes and re-creates associated authentication certificate,
// which in turn deletes all instance signatures
//
// @param owner cartodb username of the template owner
//
// @param tpl_id template identifier as returned by addTemplate
//
// @param template layergroup template, see
//        http://github.com/CartoDB/Windshaft-cartodb/wiki/Template-maps#template-format
//
// @param callback function(err)
//
TemplateMaps.prototype.updTemplate = function (owner, tpl_id, template, callback) {
    template = templateDefaults(template);

    var invalidError = this._checkInvalidTemplate(template);
    if (invalidError) {
        return callback(invalidError);
    }

    if (tpl_id !== template.name) {
        return callback(new Error(`Cannot update name of a map template ('${tpl_id}' != '${template.name}')`));
    }

    var userTemplatesKey = this.key_usr_tpl({ owner });

    this._redisCmd('HGET', [userTemplatesKey, tpl_id], (err, beforeUpdateTemplate) => {
        if (err) {
            return callback(err);
        }

        if (!beforeUpdateTemplate) {
            return callback(new Error(`Template '${tpl_id}' of user '${owner}' does not exist`));
        }

        let templateString;
        try {
            templateString = JSON.stringify(template);
        } catch (error) {
            return callback(error);
        }

        this._redisCmd('HSET', [userTemplatesKey, template.name, templateString], (err, didSetNewField) => {
            if (err) {
                return callback(err);
            }

            if (didSetNewField) {
                debug('New template created on update operation');
            }

            let beforeUpdateTemplateObject;
            try {
                beforeUpdateTemplateObject = JSON.parse(beforeUpdateTemplate);
            } catch (error) {
                return callback(error);
            }

            if (this.fingerPrint(beforeUpdateTemplateObject) !== this.fingerPrint(template)) {
                this.emit('update', owner, template.name, template);
            }

            return callback(null, template);
        });
    });
};

// List user templates
//
// @param owner cartodb username of the templates owner
//
// @param callback function(err, tpl_id_list)
//        Returns a list of template identifiers
//
TemplateMaps.prototype.listTemplates = function (owner, callback) {
    this._redisCmd('HKEYS', [this.key_usr_tpl({ owner: owner })], callback);
};

// Get a templates
//
// @param owner cartodb username of the template owner
//
// @param tpl_id template identifier as returned
//        by addTemplate or listTemplates
//
// @param callback function(err, template)
//        Return full template definition
//
TemplateMaps.prototype.getTemplate = function (owner, tpl_id, callback) {
    this._redisCmd('HGET', [this.key_usr_tpl({ owner: owner }), tpl_id], (err, template) => {
        if (err) {
            return callback(err);
        }

        let templateObject;
        try {
            templateObject = JSON.parse(template);
        } catch (error) {
            return callback(error);
        }

        return callback(null, templateObject);
    });
};

TemplateMaps.prototype.isAuthorized = function (template, authTokens) {
    if (!template) {
        return false;
    }

    authTokens = _.isArray(authTokens) ? authTokens : [authTokens];

    var templateAuth = template.auth;

    if (!templateAuth) {
        return false;
    }

    if (_.isString(templateAuth) && templateAuth === 'open') {
        return true;
    }

    if (templateAuth.method === 'open') {
        return true;
    }

    if (templateAuth.method === 'token') {
        return _.intersection(templateAuth.valid_tokens, authTokens).length > 0;
    }

    return false;
};

// Perform placeholder substitutions on a template
//
// @param template a template object (will not be modified)
//
// @param params an object containing named subsitution parameters
//        Only the ones found in the template's placeholders object
//        will be used, with missing ones taking default values.
//
// @returns a layergroup configuration
//
// @throws Error on malformed template or parameter
//
var _reNumber = /^([-+]?[\d\.]?\d+([eE][+-]?\d+)?)$/;
var _reCSSColorName = /^[a-zA-Z]+$/;
var _reCSSColorVal = /^#[0-9a-fA-F]{3,6}$/;

function _replaceVars (str, params) {
    // Construct regular expressions for each param
    Object.keys(params).forEach(function (k) {
        str = str.replace(new RegExp('<%=\\s*' + k + '\\s*%>', 'g'), params[k]);
    });
    return str;
}

function isObject (val) {
    return (_.isObject(val) && !_.isArray(val) && !_.isFunction(val));
}

TemplateMaps.prototype.instance = function (template, params) {
    var all_params = {};
    var phold = template.placeholders || {};
    Object.keys(phold).forEach(function (k) {
        var val = params.hasOwnProperty(k) ? params[k] : phold[k].default;
        var type = phold[k].type;
        // properly escape
        if (type === 'sql_literal') {
            // duplicate any single-quote
            val = val.replace(/'/g, "''");
        } else if (type === 'sql_ident') {
            // duplicate any double-quote
            val = val.replace(/"/g, '""');
        } else if (type === 'number') {
            // check it's a number
            if (typeof (val) !== 'number' && !val.match(_reNumber)) {
                throw new Error("Invalid number value for template parameter '" + k + "': " + val);
            }
        } else if (type === 'css_color') {
            // check it only contains letters or
            // starts with # and only contains hexdigits
            if (!val.match(_reCSSColorName) && !val.match(_reCSSColorVal)) {
                throw new Error("Invalid css_color value for template parameter '" + k + "': " + val);
            }
        } else {
            // NOTE: should be checked at template create/update time
            throw new Error("Invalid placeholder type '" + type + "'");
        }
        all_params[k] = val;
    });

    // NOTE: we're deep-cloning the layergroup here
    var layergroup = JSON.parse(JSON.stringify(template.layergroup));

    if (layergroup.buffersize && isObject(layergroup.buffersize)) {
        Object.keys(layergroup.buffersize).forEach(function (k) {
            layergroup.buffersize[k] = parseInt(_replaceVars(layergroup.buffersize[k], all_params), 10);
        });
    }

    for (var i = 0; i < layergroup.layers.length; ++i) {
        var lyropt = layergroup.layers[i].options;

        if (params.styles && params.styles[i]) {
        // dynamic styling for this layer
            lyropt.cartocss = params.styles[i];
        } else if (lyropt.cartocss) {
            lyropt.cartocss = _replaceVars(lyropt.cartocss, all_params);
        }
        if (lyropt.sql) {
            lyropt.sql = _replaceVars(lyropt.sql, all_params);
        }
    // Anything else ?
    }

    // extra information about the template
    layergroup.template = {
        name: template.name,
        auth: template.auth
    };

    return layergroup;
};

// Return a fingerPrint of the object
TemplateMaps.prototype.fingerPrint = function (template) {
    return crypto.createHash('md5')
        .update(JSON.stringify(template))
        .digest('hex')
    ;
};

module.exports.templateName = function templateName (templateId) {
    var templateIdTokens = templateId.split('@');
    var name = templateIdTokens[0];

    if (templateIdTokens.length > 1) {
        name = templateIdTokens[1];
    }

    return name;
};