/*jshint node:true */
"use strict";

var rootResource = require("./root"),
	httpStatus = require("./httpStatus");


function instanciate() {
	var root = rootResource();

	function yarm(options) {
		options = options || {};
		options.defaultLimit = options.defaultLimit || 10;
		options.errorStack = options.errorStack || false;


		function handleError(req, res, err) {
			if (err) {
				res.status(err.code || 500)
					.send(options.errorStack ? err.stack : err.message);
				return true;
			}
		}

		function makeCallback(req, res) {
			function cb(err, body, mime) {
				if (!handleError(req, res, err)) {
					sendResponse(req, res, body, mime);
				}
			}

			cb.file = function(err, path, mime) {
				if (!handleError(req, res, err)) {
					sendFile(req, res, path, mime);
				}
			};

			cb.status = function(code, body) {
				handleError(req, res, httpStatus(code, body));
			};

			cb.list = function(counter, lister) {
				sendListResponse(req, res, counter, lister);
			};

			cb.custom = function(handler) {
				handler(req, res);
			};

			httpStatus.names.forEach(function(name) {
				cb[name] = function() {
					handleError(req, res, httpStatus[name]());
				};
			});

			return cb;
		}

		function sendFile(req, res, path, mime) {
			if (mime) {
				res.type(mime);
			}

			res.sendFile(path);
		}


		function sendResponse(req, res, body, mime) {
			if (body === null || body === undefined) {
				handleError(req, res, httpStatus.noContent());
				return;
			}

			if (mime) {
				res.type(mime);
			}

			if (typeof body === "number") {
				// Cast to string to avoid mistaking body for HTTP status
				body = "" + body;
			}

			// TODO look for a cleaner way to identify Readables
			if (body && typeof body._read === "function") {
				body.pipe(res);
			} else if (body) {
				res.send(body);
			}
		}


		function sendListResponse(req, res, counter, lister) {
			var skip = parseInt(req.query["skip"], 10),
				limit = parseInt(req.query["limit"], 10);

			if (isNaN(skip)) {
				skip = 0;
			}

			if (isNaN(limit)) {
				limit = options.defaultLimit;
			}

			counter(req, function(err, count) {
				if (handleError(req, res, err)) {
					return;
				}

				lister(req, skip, limit, function(err, items) {
					if (handleError(req, res, err)) {
						return;
					}

					res.send({
						_count: count,
						_items: items
					});
				});
			});
		}


		function restResult(req, res, handlers) {
			var method = req.method.toUpperCase();

			switch(method) {
				case "GET":
				case "HEAD":
					if (handlers.get) {
						return handlers.get(req, makeCallback(req, res));
					} else if (handlers.count && handlers.list) {
						return sendListResponse(req, res, handlers.count, handlers.list);
					}

					break;

				case "PUT":
				case "PATCH":
					if (handlers.put) {
						return handlers.put(req, method === "PATCH", makeCallback(req, res));
					}

					break;

				case "DELETE":
					if (handlers.del) {
						return handlers.del(req, makeCallback(req, res));
					}

					break;

				case "POST":
					if (handlers.post) {
						return handlers.post(req, makeCallback(req, res));
					}

					break;

			}

			(makeCallback(req, res)).methodNotAllowed();
		}

		return function(req, res) {
			var data = root.match(req);

			function nextHook(err) {
				setImmediate(function() {
					if (err) {
						handleError(req, res, err);
						return;
					}

					var hook = data.hooks.shift();

					if (hook) {
						try {
							hook.call(null, req, nextHook);
						} catch(e) {
							nextHook(e);
						}
					} else {
						restResult(req, res, data.spec);
					}
				});
			}

			nextHook.status = function(code, body) {
				handleError(req, res, httpStatus(code, body));
			};

			httpStatus.names.forEach(function(name) {
				nextHook[name] = function() {
					nextHook(httpStatus[name]());
				};
			});

			if (data && data.spec) {
				data.hooks = data.hooks || [];
				nextHook();
			} else {
				handleError(req, res, httpStatus.notFound());
			}
		};
	}


	/* Resource definers */
	yarm.resource = function(name) {
		return root.sub(name);
	};
	yarm.remove = function(name) {
		root.remove(name);
	};


	/* Extension helper */
	yarm.extend = function(name, handler) {
		if (name in yarm) {
			throw new Error("Yarm extension '" + name + "' is already defined");
		}

		yarm[name] = handler.bind(root);
	};

	return yarm;
}


module.exports = instanciate;