/*
Basic HTTP/1.1 client request handler
*/

const int DEFAULT_SERVER_PORT = 80
const int DEFAULT_SECURE_PORT = 443
const char DEFAULT_RESOURCE[] = "/"
const char DEFAULT_PROTOCOL[] = "http"

data ResourceParts{
	char protocol[]
	char hostName[]
	int  hostPort
	char resource[]
	}

component provides HTTPRequest requires io.Output out, net.TCPSocket, net.TLS, net.TLSContext, net.dns.DNS dns, data.StringUtil stringUtil, data.IntUtil intUtil {
	
	String[] splitString(char string[], char with[])
		{
		int ndx
		
		if ((ndx = stringUtil.find(string, with)) != StringUtil.NOT_FOUND)
			{
			return new String[](new String(stringUtil.subString(string, 0, ndx)), new String(stringUtil.subString(string, ndx+1, string.arrayLength - (ndx+1))))
			}
		
		return new String[](new String(string))
		}
	
	char[] readHeaderLine(Stream socket)
		{
		char buf[]
		char last2[] = new char[2]
		
		while (last2 != "\r\n")
			{
			char b[] = socket.recv(1)
			buf = new char[](buf, b)
			last2[0] = last2[1]
			last2[1] = b[0]
			}
		
		return buf
		}
	
	Header[] readHeaders(Stream socket)
		{
		Header headers[]
		
		char buf[]
		char last4[] = new char[4]
		
		while (last4 != "\r\n\r\n")
			{
			char b[] = socket.recv(1)
			if (b == null) throw new Exception("remote connection terminated before full response received")
			buf = new char[](buf, b)
			last4[0] = last4[1]
			last4[1] = last4[2]
			last4[2] = last4[3]
			last4[3] = b[0]
			}
		
		String lines[] = stringUtil.explode(buf, "\r\n")
		
		headers = new Header[](new Header("response", lines[0].string))
		
		for (int i = 1; i < lines.arrayLength; i++)
			{
			int ndx = stringUtil.find(lines[i].string, ":") + 1
			char key[] = stringUtil.subString(lines[i].string, 0, ndx - 1)
			char value[] = stringUtil.trim(stringUtil.subString(lines[i].string, ndx, lines[i].string.arrayLength - ndx))
			
			headers = new Header[](headers, new Header(stringUtil.lowercase(key), value))
			}
		
		return headers
		}
	
	char[] getHeaderValue(Header headers[], char key[])
		{
		for (int i = 0; i < headers.arrayLength; i++)
			{
			if (headers[i].key == key)
				return headers[i].value
			}
		
		return null
		}
	
	int hexToInt(char hex[])
		{
		int result = 0
		hex = stringUtil.lowercase(hex)
		
		for (int i = 0; i < hex.arrayLength; i++)
			{
			result = result << 4
			
			if (hex[i] == "0") result += 0
			else if (hex[i] == "1") result += 1
			else if (hex[i] == "2") result += 2
			else if (hex[i] == "3") result += 3
			else if (hex[i] == "4") result += 4
			else if (hex[i] == "5") result += 5
			else if (hex[i] == "6") result += 6
			else if (hex[i] == "7") result += 7
			else if (hex[i] == "8") result += 8
			else if (hex[i] == "9") result += 9
			else if (hex[i] == "a") result += 10
			else if (hex[i] == "c") result += 12
			else if (hex[i] == "b") result += 11
			else if (hex[i] == "d") result += 13
			else if (hex[i] == "e") result += 14
			else if (hex[i] == "f") result += 15
			}
		
		return result
		}
	
	char[] readContent(Stream s, Header headers[])
		{
		char content[]
		
		if (getHeaderValue(headers, "content-length") != null)
			{
			int size = intUtil.intFromString(getHeaderValue(headers, "content-length"))

			content = s.recv(size)
			}
			else if (getHeaderValue(headers, "transfer-encoding") == "chunked")
			{
			//format: [;fields]\r\n\r\n

			bool done = false
			while (!done)
				{
				char hdr[] = stringUtil.trim(readHeaderLine(s))
				
				String tokens[] = stringUtil.explode(hdr, ";")
				
				int chunkSize = hexToInt(stringUtil.trim(tokens[0].string))

				if (chunkSize == 0)
					{
					s.recv(2)
					done = true
					}
					else
					{
					char chunk[] = s.recv(chunkSize)
					content = new char[](content, chunk)
					s.recv(2)
					}
				}
			
			}
		
		return content
		}
	
	ResourceParts parseResource(char url[], bool secure)
		{
		//parse a URL in the format [protocol://]hostname[:port][/path/to/resource]
		ResourceParts result
		
		if (!secure)
			result = new ResourceParts(DEFAULT_PROTOCOL, "", DEFAULT_SERVER_PORT, DEFAULT_RESOURCE)
			else
			result = new ResourceParts(DEFAULT_PROTOCOL, "", DEFAULT_SECURE_PORT, DEFAULT_RESOURCE)
		
		int ndx = 0
		if ((ndx = stringUtil.find(url, "://")) != StringUtil.NOT_FOUND)
			{
			result.protocol = stringUtil.subString(url, 0, ndx)
			url = stringUtil.subString(url, ndx + 3, url.arrayLength - (ndx+3))
			}
		
		if ((ndx = stringUtil.find(url, "/")) != StringUtil.NOT_FOUND)
			{
			result.hostName = stringUtil.subString(url, 0, ndx)
			url = stringUtil.subString(url, ndx, url.arrayLength - ndx)
			
			result.resource = url
			}
			else
			{
			result.hostName = url
			}
		
		//check for a port number, but make sure we're not matching against "::" in IPv6 addresses
		if ((ndx = stringUtil.rfind(result.hostName, ":")) != StringUtil.NOT_FOUND && (ndx != 0 && result.hostName[ndx-1] != ":"))
			{
			char tmp[] = result.hostName
			result.hostName = stringUtil.subString(tmp, 0, ndx)
			result.hostPort = intUtil.intFromString(stringUtil.subString(tmp, ndx+1, tmp.arrayLength - (ndx+1)))
			}
		
		return result
		}
	
	HTTPResponse handleRequest(char url[], Header headers[], char method[], char postData[], bool secure) {
		//look up host address of URL and extract the resource path being requested
		ResourceParts parts = parseResource(url, secure)
		
		char resource[] = parts.resource
		char serverIP[] = dns.getHostIP(parts.hostName)
		if (parts.protocol == "https") secure = true

		//construct the request message, including a "host" field if none is provided
		char request[] = "$method $resource HTTP/1.1\r\n"
		bool hostIncluded = false
		for (int i = 0; i < headers.arrayLength; i++) {
			if (stringUtil.lowercase(headers[i].key) == "host") { hostIncluded = true }
			request = new char[](request, headers[i].key, ":", headers[i].value, "\r\n")
		}
		if (method == "POST") {
			request = new char[](request, "content-length", ":", intUtil.makeString(postData.arrayLength), "\r\n")
		}
		if (!hostIncluded) { request = new char[](request, "host:$(parts.hostName)\r\n") }
		request = new char[](request, "\r\n")
		if (method == "POST") {
			request = new char[](request, postData)
		}
		
		//connect to server and send request
		Stream stream
		TLS tls
		TLSContext ctx
		TCPSocket s = new TCPSocket()
		if (s.connect(serverIP, parts.hostPort)) {
			stream = s
			if (secure)
				{
				ctx = new TLSContext(TLSContext.CLIENT)
				ctx.setCipherSet(TLSContext.CIPHER_DEFAULT)
				tls = new TLS(ctx)
				if (tls.connect(s) == false)
					{
					throw new Exception("Could not establish secure connection to host '$(serverIP)', port '$(parts.hostPort)'")
					}
				stream = tls
				}
			stream.send(request)
			headers = readHeaders(stream)
			char content[] = readContent(stream, headers)
			s.disconnect()
			//for convenience here we parse the response line into code/message, and we also extract the content type
			char responseCode[] = ""
			char responseMessage[] = ""
			String split[]
			if ((split = splitString(getHeaderValue(headers, "response"), " ")).arrayLength == 2
				&& (split = splitString(split[1].string, " ")).arrayLength == 2) {
				responseCode = split[0].string
				responseMessage = split[1].string
			}
			return new HTTPResponse(url, responseCode, responseMessage, content, 
				getHeaderValue(headers, "content-type"), headers)
		} else {
			throw new Exception("Could not connect to host")
		}
	}

	HTTPResponse HTTPRequest:get(char url[], opt Header headers[], bool secure) {
		return handleRequest(url, headers, "GET", null, secure)
	}

	HTTPResponse HTTPRequest:post(char url[], Header headers[], char postData[], opt bool secure) {
		return handleRequest(url, headers, "POST", postData, secure)
	}
}