const _ = require('lodash');
const Promise = require('bluebird');
const models = require('../../models');
const errors = require('@tryghost/errors');
const tpl = require('@tryghost/tpl');
const providers = require('./providers');
const parseContext = require('./parse-context');
const actionsMap = require('./actions-map-cache');

const messages = {
    noPermissionToAction: 'You do not have permission to perform this action',
    noActionsMapFoundError: 'No actions map found, ensure you have loaded permissions into database and then call permissions.init() before use.'
};

let canThis;
let CanThisResult;

// Base class for canThis call results
CanThisResult = function () {
};

CanThisResult.prototype.buildObjectTypeHandlers = function (objTypes, actType, context, permissionLoad) {
    const objectTypeModelMap = {
        post: models.Post,
        role: models.Role,
        user: models.User,
        permission: models.Permission,
        setting: models.Settings,
        invite: models.Invite,
        integration: models.Integration
    };

    // Iterate through the object types, i.e. ['post', 'tag', 'user']
    return _.reduce(objTypes, function (objTypeHandlers, objType) {
        // Grab the TargetModel through the objectTypeModelMap
        const TargetModel = objectTypeModelMap[objType];

        // Create the 'handler' for the object type;
        // the '.post()' in canThis(user).edit.post()
        objTypeHandlers[objType] = function (modelOrId, unsafeAttrs) {
            let modelId;
            unsafeAttrs = unsafeAttrs || {};

            // If it's an internal request, resolve immediately
            if (context.internal) {
                return Promise.resolve();
            }

            if (_.isNumber(modelOrId) || _.isString(modelOrId)) {
                // It's an id already, do nothing
                modelId = modelOrId;
            } else if (modelOrId) {
                // It's a model, get the id
                modelId = modelOrId.id;
            }
            // Wait for the user loading to finish
            return permissionLoad.then(function (loadedPermissions) {
                // Iterate through the user permissions looking for an affirmation
                const userPermissions = loadedPermissions.user ? loadedPermissions.user.permissions : null;

                const apiKeyPermissions = loadedPermissions.apiKey ? loadedPermissions.apiKey.permissions : null;
                let hasUserPermission;
                let hasApiKeyPermission;

                const checkPermission = function (perm) {
                    let permObjId;

                    // Look for a matching action type and object type first
                    if (perm.get('action_type') !== actType || perm.get('object_type') !== objType) {
                        return false;
                    }

                    // Grab the object id (if specified, could be null)
                    permObjId = perm.get('object_id');

                    // If we didn't specify a model (any thing)
                    // or the permission didn't have an id scope set
                    // then the "thing" has permission
                    if (!modelId || !permObjId) {
                        return true;
                    }

                    // Otherwise, check if the id's match
                    // TODO: String vs Int comparison possibility here?
                    return modelId === permObjId;
                };

                if (loadedPermissions.user && _.some(loadedPermissions.user.roles, {name: 'Owner'})) {
                    hasUserPermission = true;
                } else if (!_.isEmpty(userPermissions)) {
                    hasUserPermission = _.some(userPermissions, checkPermission);
                }

                // Check api key permissions if they were passed
                hasApiKeyPermission = true;
                if (!_.isNull(apiKeyPermissions)) {
                    // api key request have no user, but we want the user permissions checks to pass
                    hasUserPermission = true;
                    hasApiKeyPermission = _.some(apiKeyPermissions, checkPermission);
                }

                // Offer a chance for the TargetModel to override the results
                if (TargetModel && _.isFunction(TargetModel.permissible)) {
                    return TargetModel.permissible(
                        modelId, actType, context, unsafeAttrs, loadedPermissions, hasUserPermission, hasApiKeyPermission
                    );
                }

                if (hasUserPermission && hasApiKeyPermission) {
                    return;
                }

                return Promise.reject(new errors.NoPermissionError({message: tpl(messages.noPermissionToAction)}));
            });
        };

        return objTypeHandlers;
    }, {});
};

CanThisResult.prototype.beginCheck = function (context) {
    const self = this;
    let userPermissionLoad;
    let apiKeyPermissionLoad;
    let permissionsLoad;

    // Get context.user, context.api_key and context.app
    context = parseContext(context);

    if (actionsMap.empty()) {
        throw new errors.GhostError({message: tpl(messages.noActionsMapFoundError)});
    }

    // Kick off loading of user permissions if necessary
    if (context.user) {
        userPermissionLoad = providers.user(context.user);
    } else {
        // Resolve null if no context.user to prevent db call
        userPermissionLoad = Promise.resolve(null);
    }

    // Kick off loading of api key permissions if necessary
    if (context.api_key) {
        apiKeyPermissionLoad = providers.apiKey(context.api_key.id);
    } else {
        // Resolve null if no context.api_key
        apiKeyPermissionLoad = Promise.resolve(null);
    }

    // Wait for both user and app permissions to load
    permissionsLoad = Promise.all([userPermissionLoad, apiKeyPermissionLoad]).then(function (result) {
        return {
            user: result[0],
            apiKey: result[1]
        };
    });

    // Iterate through the actions and their related object types
    _.each(actionsMap.getAll(), function (objTypes, actType) {
        // Build up the object type handlers;
        // the '.post()' parts in canThis(user).edit.post()
        const objTypeHandlers = self.buildObjectTypeHandlers(objTypes, actType, context, permissionsLoad);

        // Define a property for the action on the result;
        // the '.edit' in canThis(user).edit.post()
        Object.defineProperty(self, actType, {
            writable: false,
            enumerable: false,
            configurable: false,
            value: objTypeHandlers
        });
    });

    // Return this for chaining
    return this;
};

canThis = function (context) {
    const result = new CanThisResult();

    return result.beginCheck(context);
};

module.exports = canThis;