var URL = require('url')
  , request = require('request')
  , Stream = require('stream')
  , zlib = require('zlib')
  , Error = require('http-errors')
  , mystreams = require('./streams')
  , Logger = require('./logger')
  , utils = require('./utils')
  , parse_interval = require('./config').parse_interval
  , encode = encodeURIComponent

//
// Implements Storage interface
// (same for storage.js, local-storage.js, up-storage.js)
//
function Storage(config, mainconfig) {
	if (!(this instanceof Storage)) return new Storage(config)
	this.config = config
	this.failed_requests = 0
	this.userAgent = mainconfig.user_agent
	this.ca = config.ca
	this.logger = Logger.logger.child({sub: 'out'})
	this.server_id = mainconfig.server_id

	this.url = URL.parse(this.config.url)
	if (this.url.hostname === 'registry.npmjs.org') {
		// npm registry is too slow working with ssl :(
		/*if (this.config._autogenerated) {
			// encrypt all the things!
			this.url.protocol = 'https'
			this.config.url = URL.format(this.url)
		}*/
	}

	_setupProxy.call(this, this.url.hostname, config, mainconfig, this.url.protocol === 'https:')

	this.config.url = this.config.url.replace(/\/$/, '')
	if (Number(this.config.timeout) >= 1000) {
		this.logger.warn('Too big timeout value: ' + this.config.timeout + '\nWe changed time format to nginx-like one\n(see http://wiki.nginx.org/ConfigNotation)\nso please update your config accordingly')
	}

	// a bunch of different configurable timers
	this.maxage =       parse_interval(config_get('maxage'      , '2m' ))
	this.timeout =      parse_interval(config_get('timeout'     , '30s'))
	this.max_fails =            Number(config_get('max_fails'   ,  2   ))
	this.fail_timeout = parse_interval(config_get('fail_timeout', '5m' ))
	return this

	// just a helper (`config[key] || default` doesn't work because of zeroes)
	function config_get(key, def) {
		return config[key] != null ? config[key] : def
	}
}

function _setupProxy(hostname, config, mainconfig, isHTTPS) {
	var no_proxy
	var proxy_key = isHTTPS ? 'https_proxy' : 'http_proxy'

	// get http_proxy and no_proxy configs
	if (proxy_key in config) {
		this.proxy = config[proxy_key]
	} else if (proxy_key in mainconfig) {
		this.proxy = mainconfig[proxy_key]
	}
	if ('no_proxy' in config) {
		no_proxy = config.no_proxy
	} else if ('no_proxy' in mainconfig) {
		no_proxy = mainconfig.no_proxy
	}

	// use wget-like algorithm to determine if proxy shouldn't be used
	if (hostname[0] !== '.') hostname = '.' + hostname
	if (typeof(no_proxy) === 'string' && no_proxy.length) {
		no_proxy = no_proxy.split(',')
	}
	if (Array.isArray(no_proxy)) {
		for (var i=0; i<no_proxy.length; i++) {
			var no_proxy_item = no_proxy[i]
			if (no_proxy_item[0] !== '.') no_proxy_item = '.' + no_proxy_item
			if (hostname.lastIndexOf(no_proxy_item) === hostname.length - no_proxy_item.length) {
				if (this.proxy) {
					this.logger.debug({url: this.url.href, rule: no_proxy_item},
						'not using proxy for @{url}, excluded by @{rule} rule')
					this.proxy = false
				}
				break
			}
		}
	}

	// if it's non-string (i.e. "false"), don't use it
	if (typeof(this.proxy) !== 'string') {
		delete this.proxy
	} else {
		this.logger.debug({url: this.url.href, proxy: this.proxy},
			'using proxy @{proxy} for @{url}')
	}
}

Storage.prototype.request = function(options, cb) {
	if (!this.status_check()) {
		var req = new Stream.Readable()
		process.nextTick(function() {
			if (typeof(cb) === 'function') cb(Error('uplink is offline'))
			req.emit('error', Error('uplink is offline'))
		})
		// preventing 'Uncaught, unspecified "error" event'
		req.on('error', function(){})
		return req
	}

	var self = this
	  , headers = options.headers || {}
	headers['Accept'] = headers['Accept'] || 'application/json'
	headers['Accept-Encoding'] = headers['Accept-Encoding'] || 'gzip'
	headers['User-Agent'] = headers['User-Agent'] || this.userAgent

	var method = options.method || 'GET'
	  , uri = options.uri_full || (this.config.url + options.uri)
	self.logger.info({
		method: method,
		headers: headers,
		uri: uri,
	}, "making request: '@{method} @{uri}'")

	if (utils.is_object(options.json)) {
		var json = JSON.stringify(options.json)
		headers['Content-Type'] = headers['Content-Type'] || 'application/json'
	}

	var req = request({
		url: uri,
		method: method,
		headers: headers,
		body: json,
		ca: this.ca,
		proxy: this.proxy,
		encoding: null,
		timeout: this.timeout,
	}, function(err, res, body) {
		var error
		var res_length = err ? 0 : body.length

		do_gunzip(function() {
			do_decode()
			do_log()
			if (cb) cb(err, res, body)
		})

		function do_gunzip(cb) {
			if (err) return cb()
			if (res.headers['content-encoding'] !== 'gzip') return cb()
			zlib.gunzip(body, function(er, buf) {
				if (er) err = er
				body = buf
				return cb()
			})
		}

		function do_decode() {
			if (err) {
				error = err.message
				return
			}

			if (options.json && res.statusCode < 300) {
				try {
					body = JSON.parse(body.toString('utf8'))
				} catch(_err) {
					body = {}
					err = _err
					error = err.message
				}
			}

			if (!err && utils.is_object(body)) {
				if (typeof(body.error) === 'string') {
					error = body.error
				}
			}
		}

		function do_log() {
			var message = '@{!status}, req: \'@{request.method} @{request.url}\''
			if (error) {
				message += ', error: @{!error}'
			} else {
				message += ', bytes: @{bytes.in}/@{bytes.out}'
			}
			self.logger.warn({
				err: err,
				request: {method: method, url: uri},
				level: 35, // http
				status: res != null ? res.statusCode : 'ERR',
				error: error,
				bytes: {
					in: json ? json.length : 0,
					out: res_length || 0,
				}
			}, message)
		}
	})

	var status_called = false
	req.on('response', function(res) {
		if (!req._sinopia_aborted && !status_called) {
			status_called = true
			self.status_check(true)
		}
	})
	req.on('error', function(_err) {
		if (!req._sinopia_aborted && !status_called) {
			status_called = true
			self.status_check(false)
		}
	})
	return req
}

Storage.prototype.status_check = function(alive) {
	if (arguments.length === 0) {
		if (this.failed_requests >= this.max_fails && Math.abs(Date.now() - this.last_request_time) < this.fail_timeout) {
			return false
		} else {
			return true
		}
	} else {
		if (alive) {
			if (this.failed_requests >= this.max_fails) {
				this.logger.warn({host: this.url.host}, 'host @{host} is back online')
			}
			this.failed_requests = 0
		} else {
			this.failed_requests++
			if (this.failed_requests === this.max_fails) {
				this.logger.warn({host: this.url.host}, 'host @{host} is now offline')
			}
		}
		this.last_request_time = Date.now()
	}
}

Storage.prototype.can_fetch_url = function(url) {
	url = URL.parse(url)

	return url.protocol === this.url.protocol
	    && url.host === this.url.host
	    && url.path.indexOf(this.url.path) === 0
}

Storage.prototype.get_package = function(name, options, callback) {
	if (typeof(options) === 'function') callback = options, options = {}

	var headers = {}
	if (options.etag) {
		headers['If-None-Match'] = options.etag
		headers['Accept'] = 'application/octet-stream'
	}
	this._add_proxy_headers(options.req, headers)

	this.request({
		uri: '/' + encode(name),
		json: true,
		headers: headers,
	}, function(err, res, body) {
		if (err) return callback(err)
		if (res.statusCode === 404) {
			return callback(Error[404]("package doesn't exist on uplink"))
		}
		if (!(res.statusCode >= 200 && res.statusCode < 300)) {
			var error = Error('bad status code: ' + res.statusCode)
			error.remoteStatus = res.statusCode
			return callback(error)
		}
		callback(null, body, res.headers.etag)
	})
}

Storage.prototype.get_tarball = function(name, options, filename) {
	if (!options) options = {}
	return this.get_url(this.config.url + '/' + name + '/-/' + filename)
}

Storage.prototype.get_url = function(url) {
	var stream = new mystreams.ReadTarballStream()
	stream.abort = function() {}
	var current_length = 0, expected_length

	var rstream = this.request({
		uri_full: url,
		encoding: null,
		headers: {
			Accept: 'application/octet-stream',
		},
	})

	rstream.on('response', function(res) {
		if (res.statusCode === 404) {
			return stream.emit('error', Error[404]("file doesn't exist on uplink"))
		}
		if (!(res.statusCode >= 200 && res.statusCode < 300)) {
			return stream.emit('error', Error('bad uplink status code: ' + res.statusCode))
		}
		if (res.headers['content-length']) {
			expected_length = res.headers['content-length']
			stream.emit('content-length', res.headers['content-length'])
		}

		rstream.pipe(stream)
	})

	rstream.on('error', function(err) {
		stream.emit('error', err)
	})
	rstream.on('data', function(d) {
		current_length += d.length
	})
	rstream.on('end', function(d) {
		if (d) current_length += d.length
		if (expected_length && current_length != expected_length)
			stream.emit('error', Error('content length mismatch'))
	})
	return stream
}

Storage.prototype._add_proxy_headers = function(req, headers) {
	if (req) {
		headers['X-Forwarded-For'] = (
			(req && req.headers['x-forwarded-for']) ?
			req.headers['x-forwarded-for'] + ', ' :
			''
		) + req.connection.remoteAddress
	}

	// always attach Via header to avoid loops, even if we're not proxying
	headers['Via'] =
		(req && req.headers['via']) ?
		req.headers['via'] + ', ' :
		''

	headers['Via'] += '1.1 ' + this.server_id + ' (Sinopia)'
}

module.exports = Storage