net/http/client.go

package http

import (
	"bufio"
	"crypto/tls"
	"errors"
	"fmt"
	"io"
	"strconv"
	"strings"
)

var (
	CRLF = []byte("\r\n")
	SP   = []byte(" ")
)

func Do(method string, url string, headers []*Header) (*Response, error) {
	url = strings.TrimPrefix(url, "http://")
	url = strings.TrimPrefix(url, "https://")
	path := "/"
	arr := strings.Split(url, "/")
	if len(arr) == 2 {
		path = arr[1]
	}
	if !strings.HasPrefix(path, "/") {
		path = "/" + path
	}

	connectPath := arr[0]
	// conn, err := net.Dial("tcp", connectPath)
	conn, err := tls.Dial("tcp", connectPath, nil)
	if err != nil {
		return nil, errors.New("connect " + connectPath)
	}
	defer conn.Close()

	WriteRequest(conn, method, arr[0], path, "HTTP/1.0", headers)
	return ReadResponse(conn)
}

func WriteRequest(
	w io.Writer,
	method string,
	host string,
	path string,
	httpVersion string,
	headers []*Header,
) {
	io.WriteString(w, method)
	w.Write(SP)
	io.WriteString(w, path)
	w.Write(SP)
	io.WriteString(w, httpVersion)
	w.Write(CRLF)

	for _, header := range headers {
		WriteHeader(w, header.Name, header.Value)
	}

	// headers end
	w.Write(CRLF)

	// todo: body
}

func WriteHeader(w io.Writer, name string, value string) {
	fmt.Fprintf(w, "%s:%s", name, value)
	w.Write(CRLF)
}

func ReadResponse(r io.Reader) (*Response, error) {
	b := bufio.NewReader(r)

	if _, err := b.ReadString(' '); err != nil {
		return nil, errors.New("read httpVersion")
	}
	statusCodeStr, err := b.ReadString(' ')
	if err != nil {
		return nil, errors.New("read statusCode")
	}
	if _, err := b.ReadString('\r'); err != nil {
		return nil, errors.New("read statusName")
	}
	if _, err := b.ReadString('\n'); err != nil {
		return nil, errors.New("read LF")
	}

	statusCode, err := strconv.Atoi(statusCodeStr[:len(statusCodeStr)-1])
	if err != nil {
		return nil, errors.New("read statusCode")
	}

	headerStr := ""
	contentLengthStr := ""
	headers := []*Header{}
	for {
		headerStr, err = b.ReadString('\n')
		if err != nil {
			return nil, errors.New("read header")
		}
		if headerStr == "\r\n" {
			break
		}
		arr := strings.Split(headerStr, ": ")
		value := strings.TrimSpace(arr[1])
		header := &Header{Name: arr[0], Value: value}
		if header.Name == "Content-Length" {
			contentLengthStr = header.Value
		}
		headers = append(headers, header)
	}

	length, err := strconv.Atoi(contentLengthStr)
	if err != nil {
		return nil, errors.New("read Content-Length")
	}

	body := make([]byte, 0, length)

	for i := 0; i < length; i++ {
		r, err := b.ReadByte()
		if err != nil {
			return nil, errors.New("read body")
		}
		body = append(body, r)
	}

	return &Response{
		StatusCode: statusCode,
		Headers:    headers,
		Body:       body,
	}, nil
}