/*
Copyright 2015, 2016 OpenMarket Ltd

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
/**
 * @module pushprocessor
 */

/**
 * Construct a Push Processor.
 * @constructor
 * @param {Object} client The Matrix client object to use
 */
function PushProcessor(client) {
    var escapeRegExp = function(string) {
        return string.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
    };

    var matchingRuleFromKindSet = function(ev, kindset, device) {
        var rulekinds_in_order = ['override', 'content', 'room', 'sender', 'underride'];
        for (var ruleKindIndex = 0;
                ruleKindIndex < rulekinds_in_order.length;
                ++ruleKindIndex) {
            var kind = rulekinds_in_order[ruleKindIndex];
            var ruleset = kindset[kind];

            for (var ruleIndex = 0; ruleIndex < ruleset.length; ++ruleIndex) {
                var rule = ruleset[ruleIndex];
                if (!rule.enabled) { continue; }

                var rawrule = templateRuleToRaw(kind, rule, device);
                if (!rawrule) { continue; }

                if (ruleMatchesEvent(rawrule, ev)) {
                    rule.kind = kind;
                    return rule;
                }
            }
        }
        return null;
    };

    var templateRuleToRaw = function(kind, tprule, device) {
        var rawrule = {
            'rule_id': tprule.rule_id,
            'actions': tprule.actions,
            'conditions': []
        };
        switch (kind) {
            case 'underride':
            case 'override':
                rawrule.conditions = tprule.conditions;
                break;
            case 'room':
                if (!tprule.rule_id) { return null; }
                rawrule.conditions.push({
                    'kind': 'event_match',
                    'key': 'room_id',
                    'pattern': tprule.rule_id
                });
                break;
            case 'sender':
                if (!tprule.rule_id) { return null; }
                rawrule.conditions.push({
                    'kind': 'event_match',
                    'key': 'user_id',
                    'pattern': tprule.rule_id
                });
                break;
            case 'content':
                if (!tprule.pattern) { return null; }
                rawrule.conditions.push({
                    'kind': 'event_match',
                    'key': 'content.body',
                    'pattern': tprule.pattern
                });
                break;
        }
        if (device) {
            rawrule.conditions.push({
                'kind': 'device',
                'profile_tag': device
            });
        }
        return rawrule;
    };

    var ruleMatchesEvent = function(rule, ev) {
        var ret = true;
        for (var i = 0; i < rule.conditions.length; ++i) {
            var cond = rule.conditions[i];
            ret &= eventFulfillsCondition(cond, ev);
        }
        //console.log("Rule "+rule.rule_id+(ret ? " matches" : " doesn't match"));
        return ret;
    };

    var eventFulfillsCondition = function(cond, ev) {
        var condition_functions = {
            "event_match": eventFulfillsEventMatchCondition,
            "device": eventFulfillsDeviceCondition,
            "contains_display_name": eventFulfillsDisplayNameCondition,
            "room_member_count": eventFulfillsRoomMemberCountCondition
        };
        if (condition_functions[cond.kind]) {
            return condition_functions[cond.kind](cond, ev);
        }
        return true;
    };

    var eventFulfillsRoomMemberCountCondition = function(cond, ev) {
        if (!cond.is) { return false; }

        var room = client.getRoom(ev.room_id);
        if (!room || !room.currentState || !room.currentState.members) { return false; }

        var memberCount = Object.keys(room.currentState.members).filter(function(m) {
            return room.currentState.members[m].membership == 'join';
        }).length;

        var m = cond.is.match(/^([=<>]*)([0-9]*)$/);
        if (!m) { return false; }
        var ineq = m[1];
        var rhs = parseInt(m[2]);
        if (isNaN(rhs)) { return false; }
        switch (ineq) {
            case '':
            case '==':
                return memberCount == rhs;
            case '<':
                return memberCount < rhs;
            case '>':
                return memberCount > rhs;
            case '<=':
                return memberCount <= rhs;
            case '>=':
                return memberCount >= rhs;
            default:
                return false;
        }
    };

    var eventFulfillsDisplayNameCondition = function(cond, ev) {
        if (!ev.content || ! ev.content.body || typeof ev.content.body != 'string') {
            return false;
        }

        var room = client.getRoom(ev.room_id);
        if (!room || !room.currentState || !room.currentState.members ||
            !room.currentState.getMember(client.credentials.userId)) { return false; }

        var displayName = room.currentState.getMember(client.credentials.userId).name;

        // N.B. we can't use \b as it chokes on unicode. however \W seems to be okay
        // as shorthand for [^0-9A-Za-z_].
        var pat = new RegExp("(^|\\W)" + escapeRegExp(displayName) + "(\\W|$)", 'i');
        return ev.content.body.search(pat) > -1;
    };

    var eventFulfillsDeviceCondition = function(cond, ev) {
        return false; // XXX: Allow a profile tag to be set for the web client instance
    };

    var eventFulfillsEventMatchCondition = function(cond, ev) {
        var val = valueForDottedKey(cond.key, ev);
        if (!val || typeof val != 'string') { return false; }

        var pat;
        if (cond.key == 'content.body') {
            pat = '(^|\\W)' + globToRegexp(cond.pattern) + '(\\W|$)';
        } else {
            pat = '^' + globToRegexp(cond.pattern) + '$';
        }
        var regex = new RegExp(pat, 'i');
        return !!val.match(regex);
    };

    var globToRegexp = function(glob) {
        // From
        // https://github.com/matrix-org/synapse/blob/abbee6b29be80a77e05730707602f3bbfc3f38cb/synapse/push/__init__.py#L132
        // Because micromatch is about 130KB with dependencies,
        // and minimatch is not much better.
        var pat = escapeRegExp(glob);
        pat = pat.replace(/\\\*/, '.*');
        pat = pat.replace(/\?/, '.');
        pat = pat.replace(/\\\[(!|)(.*)\\]/, function(match, p1, p2, offset, string) {
            var first = p1 && '^' || '';
            var second = p2.replace(/\\\-/, '-');
            return '[' + first + second + ']';
        });
        return pat;
    };

    var valueForDottedKey = function(key, ev) {
        var parts = key.split('.');
        var val = ev;
        while (parts.length > 0) {
            var thispart = parts.shift();
            if (!val[thispart]) { return null; }
            val = val[thispart];
        }
        return val;
    };

    var matchingRuleForEventWithRulesets = function(ev, rulesets) {
        if (!rulesets || !rulesets.device) { return null; }
        if (ev.user_id == client.credentials.userId) { return null; }

        var allDevNames = Object.keys(rulesets.device);
        for (var i = 0; i < allDevNames.length; ++i) {
            var devname = allDevNames[i];
            var devrules = rulesets.device[devname];

            var matchingRule = matchingRuleFromKindSet(devrules, devname);
            if (matchingRule) { return matchingRule; }
        }
        return matchingRuleFromKindSet(ev, rulesets.global);
    };

    var actionListToActionsObject = function(actionlist) {
        var actionobj = { 'notify': false, 'tweaks': {} };
        for (var i = 0; i < actionlist.length; ++i) {
            var action = actionlist[i];
            if (action === 'notify') {
                actionobj.notify = true;
            } else if (typeof action === 'object') {
                if (action.value === undefined) { action.value = true; }
                actionobj.tweaks[action.set_tweak] = action.value;
            }
        }
        return actionobj;
    };

    var pushActionsForEventAndRulesets = function(ev, rulesets) {
        var rule = matchingRuleForEventWithRulesets(ev, rulesets);
        if (!rule) { return {}; }

        var actionObj = actionListToActionsObject(rule.actions);

        // Some actions are implicit in some situations: we add those here
        if (actionObj.tweaks.highlight === undefined) {
            // if it isn't specified, highlight if it's a content
            // rule but otherwise not
            actionObj.tweaks.highlight = (rule.kind == 'content');
        }

        return actionObj;
    };

    this.actionsForEvent = function(ev) {
        return pushActionsForEventAndRulesets(ev, client.pushRules);
    };
}

/**
 * @typedef {Object} PushAction
 * @type {Object}
 * @property {boolean} notify Whether this event should notify the user or not.
 * @property {Object} tweaks How this event should be notified.
 * @property {boolean} tweaks.highlight Whether this event should be highlighted
 * on the UI.
 * @property {boolean} tweaks.sound Whether this notification should produce a
 * noise.
 */

/** The PushProcessor class. */
module.exports = PushProcessor;