package bin;

import kernel.binstore.BinStore;
import kernel.ps.ProcessHandle;
import kernel.ps.Process;
import kernel.ps.ProcessManager;
import lib.Color;
import kernel.ui.WindowContext;

using tink.CoreApi;

class Terminal implements Process {
	private static inline final MAX_BACKLOG:Int = 100;

	private var handle:ProcessHandle;

	private var ctx:WindowContext;
	private var requestRender: () -> Void;
	
	private var input:String = "";
	private var backlog:Array<String> = [];
	private var history:Array<String> = [];
	private var historyIndex:Int = 0;

	private var runningPID:PID = -1; 

	public function new() {}

	public function run(handle: ProcessHandle): Void {
		this.handle = handle;

		var statelessContext = handle.createStatelessWindowContext();

		this.ctx = statelessContext.ctx;
		this.requestRender = statelessContext.requestRender;

		statelessContext.setRenderFunc(this.render);

		// Add input event handlers
		handle.addCallbackLink(this.ctx.onChar.handle(char -> {
			if (this.runningPID > 0) return;
			this.input += char;
			this.requestRender();
		}));

		// Add key event handlers
		handle.addCallbackLink(this.ctx.onKey.handle(e -> {
			switch (e.keyCode) {
				case 259: // Backspace
					if (this.runningPID > 0) return;
					this.input = this.input.substr(0, this.input.length - 1);
					this.requestRender();
				case 257: // Enter
					if (this.runningPID > 0) return;
					this.backlog.push("> " + this.input);
					var command = this.input;
					this.input = "";
					this.requestRender();
					this.historyIndex = 0;
					this.invokeCommand(command);
				case 269: // END
					this.stopCurrentPS();
				case 265: // UP
					if (this.historyIndex < this.history.length) {
						this.historyIndex++;
						this.input = this.history[this.history.length - this.historyIndex];
						this.requestRender();
					}
			}
		}));

		this.requestRender();
	}

	private function stopCurrentPS() {
		if (this.runningPID < 0) {
			return;
		}

		ProcessManager.kill(this.runningPID);
	}

	private function render() {
		var size = this.ctx.getSize();
		var linesAvailable = size.y - 1;

		var start:Int = this.backlog.length - linesAvailable;

		for (i in 0...linesAvailable) {
			var line = this.backlog[start + i];

			this.ctx.setCursorPos(0, i);
			this.ctx.clearLine();

			if (line != null) {
				this.ctx.write(line);
			}
		}

		this.ctx.setCursorPos(0, size.y - 1);
		this.ctx.clearLine();

		this.ctx.setTextColor(Color.Blue);
		this.ctx.write("> ");

		this.ctx.setTextColor(Color.White);
		this.ctx.write(this.input);

		if (this.runningPID < 0) {
			this.ctx.setCursorBlink(true);
		} else {
			this.ctx.setCursorBlink(false);
		}
	}

	private function invokeCommand(command:String):Void {
		var args = this.parseArgs(command);

		if (args.length == 0) {
			return;
		}

		this.history.push(command);

		if (this.history.length > MAX_BACKLOG) {
			this.history.shift();
		}

		var commandName = args[0];

		// Handle built-in commands
		switch (commandName) {
			case "clear":
				this.clear();
				return;
		}

		var commandArgs:Array<String> = args.slice(1);
		var hadInput = false;

		var ps = getProgByName(commandName);
		if (ps == null) {
			this.backlog.push("Unknown command: " + commandName);
			this.requestRender();
			return;
		}

		this.runningPID = ProcessManager.run(ps,{
			args: commandArgs,
			onWrite: (s:String) -> {
				if (s == "") {
					return;
				}

				if (!hadInput) {
					// Add a new line, so that the input is not on the same line as the command
					this.backlog.push("");
					hadInput = true;
				}

				for (line in s.split("\n")) {
					if (line == ""){
						this.backlog.push("");
					} else {
						this.backlog[this.backlog.length - 1] += s;
					}

					// Trim the backlog if it's too long
					if (this.backlog.length > MAX_BACKLOG) {
						this.backlog.shift();
					}
				}
				
				this.requestRender();
			},
			onExit: (success:Bool) -> {
				this.runningPID = -1;
				if (this.backlog[this.backlog.length - 1] == "") {
					this.backlog.pop();
				}

				this.requestRender();
			}
		});

		this.ctx.setCursorBlink(false);
	}

	/**
		Convter a command string into an array of arguments where the first element is the command name
	**/
	private function parseArgs(command:String):Array<String> {
		// TODO: tim and quote handling
		return command.split(" ");
	}

	private function clear() {
		this.backlog = [];
		this.requestRender();
	}

	private function getProgByName(name:String):Process {
		var bin = BinStore.getBinByAlias(name);
		if (bin == null) {
			return null;
		}

		return Type.createInstance(bin.c,[]);
	}

	private function moveCursorToInput() {
		var size = this.ctx.getSize();
		this.ctx.setCursorPos(this.input.length + 2, size.y - 1);
	}
}