/**

* Implements a simple select-replace file editor in Telegram.

* It works as follows:

*

* 1. The user invokes the editor with a non-empty file.

* 2. The contents of the file are posted as a message.

* 3. The user replies to that message with (part of) the text.

* The bot will locate that substring in the file contents and track the message.

* 4. The user edits his message.

* The bot will then replace the original substring, save the file and edit its message.

* If there are any problems with saving the file, the editor may detach.

*

* NOTE: sync I/O is used for simplicity; be careful! (TODO)

**/

var fs = require("fs");

var escapeHtml = require("escape-html");

var utils = require("./utils");

function ChunkedString(text) {

this.text = text;

this.chunks = [];

}

ChunkedString.prototype.findAcquire = function findAcquire(text) {

if (text.length == 0) throw Error("Empty find text not allowed");

var index = this.text.indexOf(text);

if (index == -1)

throw Error("The substring was not found. Wrapping in tildes may be necessary.");

if (index != this.text.lastIndexOf(text))

throw Error("There are multiple instances of the passed substring");

return this.acquire(index, text.length);

};

ChunkedString.prototype.acquire = function acquire(offset, length) {

if (offset < 0 || length <= 0 || offset + length > this.text.length)

throw Error("Invalid coordinates");

for (var i = 0; i < this.chunks.length; i++) {

var c = this.chunks[i];

if (offset + length > c.offset || c.offset + c.text.length > offset)

throw Error("Chunk overlaps");

}

var chunk = { offset: offset, text: this.text.substring(offset, offset + length) };

this.chunks.push(chunk);

return chunk;

};

ChunkedString.prototype.release = function release(chunk) {

if (this.chunks.indexOf(chunk) == -1) throw Error("Invalid chunk given");

this.chunks.splice(index, 1);

};

ChunkedString.prototype.modify = function modify(chunk, text) {

if (this.chunks.indexOf(chunk) == -1) throw Error("Invalid chunk given");

if (text.length == 0) throw Error("Empty replacement not allowed");

var end = chunk.offset + chunk.text.length;

this.text = this.text.substring(0, chunk.offset) + text + this.text.substring(end);

var diff = text.length - chunk.text.length;

chunk.text = text;

this.chunks.forEach(function (c) {

if (c.offset > chunk.offset) c.offset += diff;

});

};

function Editor(reply, file, encoding) {

if (!encoding) encoding = "utf-8";

this.reply = reply;

this.file = file;

this.encoding = encoding;

// TODO: support for longer files (paginated, etc.)

// FIXME: do it correctly using fd, keeping it open

var contents = fs.readFileSync(file, encoding);

if (contents.length > 1500 || contents.split("\n") > 50)

throw Error("The file is too long");

this.contents = new ChunkedString(contents);

this.chunks = {}; // associates each message ID to an active chunk

this.message = new utils.EditedMessage(reply, this._render(), "HTML");

this.fileTouched = false;

}

Editor.prototype._render = function _render() {

if (!this.contents.text.trim()) return "<em>(empty file)</em>";

return "<pre>" + escapeHtml(this.contents.text) + "</pre>";

};

Editor.prototype.handleReply = function handleReply(msg) {

this.message.idPromise.then(function (id) {

if (this.detached) return;

if (msg.reply.id != id) return;

try {

this.chunks[msg.id] = this.contents.findAcquire(msg.text);

} catch (e) {

this.reply.html("%s", e.message);

}

}.bind(this));

};

Editor.prototype.handleEdit = function handleEdit(msg) {

if (this.detached) return false;

if (!Object.hasOwnProperty.call(this.chunks, msg.id)) return false;

this.contents.modify(this.chunks[msg.id], msg.text);

this.attemptSave();

return true;

};

Editor.prototype.attemptSave = function attemptSave() {

this.fileTouched = true;

process.nextTick(function () {

if (!this.fileTouched) return;

if (this.detached) return;

this.fileTouched = false;

// TODO: check for file external modification, fail then

try {

fs.writeFileSync(this.file, this.contents.text, this.encoding);

} catch (e) {

this.reply.html("Couldn't save file: %s", e.message);

return;

}

this.message.edit(this._render());

}.bind(this));

};

Editor.prototype.detach = function detach() {

this.detached = true;

};

module.exports.Editor = Editor;