package upgrade

import (
	"bytes"
	"fmt"
	"strings"
)

// HeaderType represents all 'valid' HTTP request headers
type HeaderType uint8

// header types
const (
	Unknown HeaderType = iota
	Host
	Upgrade
	Connection
	Origin
	WSKey
	WSProtocol
	WSExtensions
	WSVersion
)

// HeaderValue represents a unique or multiple header value(s)
type HeaderValue [][]byte

// Header represents the data of a HTTP request header
type Header struct {
	Name   HeaderType
	Values HeaderValue
}

// ReadHeader tries to parse an HTTP header from a byte array
func ReadHeader(b []byte) (*Header, error) {

	// 1. Split by ':'
	parts := bytes.Split(b, []byte(": "))

	if len(parts) != 2 {
		return nil, fmt.Errorf("invalid HTTP header format '%s'", b)
	}

	// 2. Create instance
	inst := &Header{}

	// 3. Check for header name
	switch strings.ToLower(string(parts[0])) {
	case "host":
		inst.Name = Host
	case "upgrade":
		inst.Name = Upgrade
	case "connection":
		inst.Name = Connection
	case "origin":
		inst.Name = Origin
	case "sec-websocket-key":
		inst.Name = WSKey
	case "sec-websocket-protocol":
		inst.Name = WSProtocol
	case "sec-websocket-extensions":
		inst.Name = WSExtensions
	case "sec-websocket-version":
		inst.Name = WSVersion
	default:
		inst.Name = Unknown
	}

	// 4. Split values
	inst.Values = bytes.Split(parts[1], []byte(", "))

	return inst, nil

}