// Copyright (c) 2022 Nadeen Udantha <me@nadeen.lk>. All rights reserved.

package boihttp

import (
	"bufio"
	"bytes"
	"io"
	"strconv"
)

const (
	VersionHTTP1_0 = "HTTP/1.0"
	VersionHTTP1_1 = "HTTP/1.1"
)

// https://datatracker.ietf.org/doc/html/rfc2616#section-4
type Message struct {
	StatusCode                    int
	Version, Method, Path, Status string
	Headers
}

func (m *Message) SetStatus(code int, status string) {
	m.Status = status
	m.StatusCode = code
}

var EmptyBody io.Reader = &emptyBody{}

type emptyBody struct{}

func (l *emptyBody) Read(p []byte) (n int, err error) {
	return 0, io.EOF
}

func (m *Message) body(r *bufio.Reader) io.Reader {
	n := m.ContentLength()
	if n == 0 {
		return EmptyBody
	}
	return &io.LimitedReader{R: r, N: int64(n)}
}

func (m *Message) ReadRequest(r *bufio.Reader) error {
	return m.read(r, true)
}

func (m *Message) ReadResponse(r *bufio.Reader) error {
	return m.read(r, false)
}

func (m *Message) read(r *bufio.Reader, isRequest bool) error {
	line, err := readline(r)
	if err != nil {
		return err
	}
	parts := bytes.SplitN(line, []byte(" "), 3)
	if len(parts) != 3 {
		panic("wtf?")
	}
	if isRequest { // GET / HTTP/1.0
		m.Method, m.Path, m.Version = string(parts[0]), string(parts[1]), string(parts[2])
	} else { // HTTP/1.0 200 Noice
		m.StatusCode, err = strconv.Atoi(string(parts[1]))
		if err != nil {
			return err
		}
		m.Version, m.Status = string(parts[0]), string(parts[2])
	}
	m.Headers = make(Headers)
	n := 0
	for {
		line, err := readline(r)
		if err != nil {
			return err
		}
		if len(line) == 0 {
			break
		}
		parts = bytes.SplitN(line, []byte(": "), 2)
		if len(parts) != 2 {
			panic("wtf")
		}
		m.Add(string(parts[0]), string(parts[1]))
		n++
		if n >= 64 {
			panic("wtf?")
		}
	}
	return nil
}

func readline(r *bufio.Reader) ([]byte, error) {
	line, p, err := r.ReadLine()
	if p || len(line) > 8192 {
		panic("wtf?")
	}
	return line, err
}

const crlf = "\r\n"

func (m *Message) WriteRequest(r *bufio.Writer) error {
	return m.write(r, true)
}

func (m *Message) WriteResponse(r *bufio.Writer) error {
	return m.write(r, false)
}

func (m *Message) write(w *bufio.Writer, isRequest bool) error {
	if isRequest { // GET / HTTP/1.0
		w.WriteString(m.Method)
		w.WriteByte(' ')
		w.WriteString(m.Path)
		w.WriteByte(' ')
		w.WriteString(m.Version)
	} else { // HTTP/1.0 200 Noice
		w.WriteString(m.Version)
		w.WriteByte(' ')
		w.WriteString(strconv.Itoa(m.StatusCode))
		w.WriteByte(' ')
		w.WriteString(m.Status)
	}
	w.WriteString(crlf)
	for k, vs := range m.Headers {
		for _, v := range vs {
			w.WriteString(k)
			w.WriteString(": ")
			w.WriteString(v)
			w.WriteString(crlf)
		}
	}
	_, err := w.WriteString(crlf)
	return err
}