/*
 * IRCd Charybdis 5/Matrix
 *
 * Copyright (C) 2017 Charybdis Development Team
 * Copyright (C) 2017 Jason Volk (jason@zemos.net)
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice is present in all copies.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 */

'use strict';

/**
 *******************************************************************************
 * State Function
 *
 * Dictionary of events considered "state events." The state provides context for the
 * event horizon of a timeline (the termination point at the start) to prevent the
 * need for querying indeterminately over the horizon.
 *
 * This class allows the timeline to be the single source of
 * authority for events in the room. So long as the timeline is
 * maintained in order, the state object will always provide
 * an accurate result as to the state of a room. This proxy
 * prevents any race between the timeline and the state object.
 */
room.state = class
{
	constructor(timeline)
	{
		// The state function holds an internal reference to the timeline to make queries
		this.timeline = timeline;

		// The results of queries to the timeline are cached in the backing-object here.
		this.cache = Object.copy(room.state.defaults);

		// Cache timestamps (type => timestamp) is used to find out if the cache data is stale with
		// respect to when the timeline was last modified. This is partitioned by type even though
		// the timeline only has one TS value for now so all types are invalidated at the same time.
		this.ts = {};

		this.content = new room.state.content(this);
	}
};

room.state.prototype.set = function(state, type, val)
{
	mc.abort({message: "illegal"});
	return false;
};

room.state.prototype.get = function(state, type)
{
	if(this.valid(type))
		if((type in state))
			return state[type];

	let query = mc.event.is_type.bind(null, type);
	let idx = this.timeline.query(query);
	let event = this.timeline[idx[0]];
	if(!event || event.state_key === undefined)
		return state[type];

	this.update(type);
	return event.state_key.length? this._get_aggreg(state, type, idx):
	                               this._get_single(state, type, idx);
};

room.state.prototype._get_single = function(state, type, idx)
{
	state[type] = this.timeline[idx[0]];
	return state[type];
};

room.state.prototype._get_aggreg = function(state, type, idx)
{
	if(typeof(state[type]) != "object")
		state[type] = {};

	// Ensure true chronological order here so events that happen
	// after other events can simply overwrite them in this iteration.
	let present = this.timeline[0];
	idx.reverse().forEach((i) =>
	{
		let event = this.timeline[i];
		state[type][event.state_key] = event;
	});

	return state[type];
};

/** Determine if the state function has an up to date cache.
 */
room.state.prototype.valid = function(type)
{
	let time = this.ts[type];
	return time && time >= this.timeline.modified;
};

/** Updates the cache timestamp for type
 */
room.state.prototype.update = function(type)
{
	return this.ts[type] = mc.now();
};

/** Clears the cache for type
 *
 * After this, access to state will require new queries into the timeline.
 */
room.state.prototype.invalidate = function(type)
{
	Object.clear(this.cache[type]);
	Object.defaults(this.cache[type], room.state.defaults[type]);
	this.ts[type] = 0;
};

/**
 **************************************
 *
 * State content tree
 *
 */
room.state.content = class
{
	constructor(state, depth = 0)
	{
		this.state = state;
		this.depth = depth;
	}
};

room.state.content.prototype.set = function(state, key, val)
{
	mc.abort({message: "unimplemented"});
	return false;
};

room.state.content.prototype.get = function(state, key)
{
	for(let full in state)
	{
		let type = full.split(".");
		for(let i = 0; i < this.depth; i++)
			type.shift();

		let part = type.shift();
		if(part != key)
			continue;

		if(type.length > 0)
		{
			let handler = new room.state.content(this.state, this.depth + 1);
			return new Proxy(state, handler);
		}

		if(state[full].content)
			return state[full].content;
		else
			return Object.map(state[full], (key, event) => event.content);
	}
};

Object.defineProperty(room.state, 'defaults', {
writable: false,
enumerable: false,
configurable: false,
value:
{
	// 10.5.1: m.room.aliases - state_key'ed dictionary of aliases
	"m.room.aliases":
	{
		// "server_hostname": content.aliases
	},

	// 10.5.2: m.room.canonical_alias - main event
	"m.room.canonical_alias":
	{
		content:
		{
			alias: undefined,
		},
	},

	// 10.5.3: m.room.create - main event
	"m.room.create":
	{
		content:
		{
			creator: undefined,
		},
	},

	// 10.5.4: m.room.join_rules - main event
	"m.room.join_rules":
	{
		content:
		{
			join_rule: undefined,
		},
	},

	// 10.5.5: m.room.member - state_key'ed dictionary of members
	"m.room.member":
	{
		// "mxid": { membership: "join", displayname: "foo" },
	},

	// 10.5.6: m.room.power_levels - main event
	"m.room.power_levels":
	{
		content:
		{
			// Defaults
			events_default: 0,
			state_default: 0,
			users_default: 0,

			// Actions (10.5.6: defaults to 50 if unspecified)
			ban: 50,
			invite: 50,
			kick: 50,
			redact: 50,

			// Access maps
			events: {},           // Power level required for event type; { "m.room.type": power }
			users: {},            // Power level available to user; { mxid: power }
		},
	},

	// 11.2.1.3: m.room.name - main event
	"m.room.name":
	{
		content:
		{
			name: undefined,
		},
	},

	// 11.2.1.4: m.room.topic - main event
	"m.room.topic":
	{
		content:
		{
			topic: undefined,
		},
	},

	// 11.2.1.5: m.room.avatar - main event
	"m.room.avatar":
	{
		content:
		{
			info: {},
			url: undefined,
		},
	},

	// 11.9.1.1: m.room.history_visibility - main event
	"m.room.history_visibility":
	{
		content:
		{
			history_visibility: "shared", // 11.9.3: defaults to 'shared'
		},
	},

	// 11.13.1.1: m.room.guest_access - main event
	"m.room.guest_access":
	{
		content:
		{
			guest_access: "forbidden",
		}
	},
}});


/**
 * State -> Summary
 *
 * Digests a room's state into the format of the matrix rooms
 * directory (i.e. public state).
 *
 * Usage: room.state.summary(myroom.state)
 *
 * This is a static function, as the room's state object proxies the
 * timeline and state.public() will then query the timeline.
 */
room.state.summary = function(state)
{
	let members = state['m.room.member'];
	let is_join = (mxid) => maybe(() => members[mxid].content.membership == "join");

	let aliases = [];
	Object.each(state['m.room.aliases'], (state_key, event) =>
	{
		aliases = aliases.concat(event.content.aliases);
	});

	return {
		room_id: state['m.room.create'].room_id,
		name: state['m.room.name'].content.name,
		topic: state['m.room.topic'].content.topic,
		canonical_alias: state['m.room.canonical_alias'].content.alias,
		world_readable: state['m.room.history_visibility'].content.history_visibility == "world_readable",
		guest_can_join: state['m.room.guest_access'].content.guest_access == "can_join",
		num_joined_members: Array.count(Object.keys(members), is_join),
		aliases: aliases,
	};
};

/** Summary -> State (events)
 *
 * Translate summary data into an array of events. The events will not
 * have authentic data other than the essential content but we specify
 * an origin_server_ts of 0 indicating they should be replaced by any
 * timeline algorithm.
 */
room.state.summary.parse = function(summary)
{
	let events = [];
	Object.each(summary, (key, val) =>
	{
		let handler = room.state.summary.parse.on[key];
		if(typeof(handler) == "function") try
		{
			let ret = handler(val);
			if(typeof(ret) != "object")
				return;

			if(Array.isArray(ret))
				events = events.concat(ret);
			else
				events.push(ret);
		}
		catch(error)
		{
			console.error("Room summary parse error: key[" + key + "] " + error);
		}
		else
		{
			console.warn("Unhandled room summary key [" + key + "]");
		}
	});

	return events;
};

// Collection of handlers.
room.state.summary.parse.on = {};

room.state.summary.parse.on["room_id"] = function(room_id)
{
	return;
};

room.state.summary.parse.on["name"] = function(name)
{
	return {
		type: "m.room.name",
		origin_server_ts: 0,
		state_key: "",
		content:
		{
			name: name,
		},
	};
};

room.state.summary.parse.on["topic"] = function(topic)
{
	return {
		type: "m.room.topic",
		origin_server_ts: 0,
		state_key: "",
		content:
		{
			alias: topic,
		}
	};
};

room.state.summary.parse.on["canonical_alias"] = function(canonical_alias)
{
	return {
		type: "m.room.canonical_alias",
		origin_server_ts: 0,
		state_key: "",
		content:
		{
			alias: canonical_alias,
		}
	};
};

room.state.summary.parse.on["aliases"] = function(aliases)
{
	let contents = {};
	aliases.forEach((alias) =>
	{
		let [local, domain] = alias.split(":");
		if(!(domain in contents))
			contents[domain] = [];

		contents[domain].push(alias);
	});

	let events = [];
	Object.each(contents, (domain, aliases) =>
	{
		events.push(
		{
			type: "m.room.aliases",
			origin_server_ts: 0,
			state_key: domain,
			content:
			{
				aliases: aliases,
			},
		})
	});

	return events;
};

room.state.summary.parse.on["guest_can_join"] = function(bool)
{
	return {
		type: "m.room.guest_access",
		origin_server_ts: 0,
		state_key: "",
		content:
		{
			guest_access: bool? "can_join" : "forbidden",
		},
	};
};

room.state.summary.parse.on["world_readable"] = function(bool)
{
	return {
		type: "m.room.history_visibility",
		origin_server_ts: 0,
		state_key: "",
		content:
		{
			history_visibility: bool? "world_readable" : undefined,
		},
	};
};

room.state.summary.parse.on["num_joined_members"] = function(num_joined_members)
{
	// TODO: XXX
	return
};

/* TODO: XXX
room.state.summary.parse.on["avatar_url"] = function(avatar_url)
{
};
*/