package ircv3

import (
	"errors"
	"io"
	"strings"
)

type Message struct {
	Source  *NUH
	Command string
	Params  []string
	Tags    Tags
}

func NewMessage(command string, params ...string) *Message {
	return &Message{
		Source:  nil,
		Command: command,
		Params:  params,
		Tags:    make(Tags),
	}
}
func (m *Message) SetSource(nuh *NUH) *Message {
	m.Source = nuh
	return m
}

func (m *Message) Param(i int) string {
	if len(m.Params) > i {
		return m.Params[i]
	}
	return ""
}
func (msg *Message) String() string {
	sb := new(strings.Builder)
	msg.Encode(sb)
	return sb.String()
}

func (msg *Message) Encode(w io.Writer) error {
	if msg.Command == "" {
		return nil
	}
	if msg.Tags != nil && len(msg.Tags) > 0 {
		_, err := msg.Tags.WriteTo(w)
		if err != nil {
			return err
		}
		_, err = w.Write([]byte(" "))
		if err != nil {
			return err
		}
	}
	if msg.Source != nil {
		if _, err := w.Write([]byte(":")); err != nil {
			return err
		}
		if _, err := w.Write([]byte(msg.Source.String())); err != nil {
			return err
		}
		if _, err := w.Write([]byte(" ")); err != nil {
			return err
		}
	}
	// now write command
	if _, err := w.Write([]byte(msg.Command)); err != nil {
		return err
	}
	if len(msg.Params) > 0 {
		if _, err := w.Write([]byte(" ")); err != nil {
			return err
		}
	}
	for idx, v := range msg.Params {
		if idx != 0 {
			if _, err := w.Write([]byte(" ")); err != nil {
				return err
			}
		}
		// now write any params
		if len(msg.Params)-1 == idx && strings.Contains(v, " ") {
			if _, err := w.Write([]byte(":")); err != nil {
				return err
			}
		}
		if _, err := w.Write([]byte(v)); err != nil {
			return err
		}
	}
	return nil
}

type NUH struct {
	Name string
	User string
	Host string
}

var (
	MalformedNUH = errors.New("NUH is malformed")
)

// ParseNUH parses a NUH source of an IRC message into its constituent parts;
// name (nickname or server name), username, and hostname.
func ParseNUH(in string) (out NUH, err error) {
	if len(in) == 0 {
		return out, MalformedNUH
	}
	hostStart := strings.IndexByte(in, '@')
	if hostStart != -1 {
		out.Host = in[hostStart+1:]
		in = in[:hostStart]
	}
	userStart := strings.IndexByte(in, '!')
	if userStart != -1 {
		out.User = in[userStart+1:]
		in = in[:userStart]
	}
	out.Name = in

	return
}

// Canonical returns the canonical string representation of the NUH.
func (nuh *NUH) String() (result string) {
	var out strings.Builder
	out.Grow(len(nuh.Name) + len(nuh.User) + len(nuh.Host) + 2)
	out.WriteString(nuh.Name)
	if len(nuh.User) != 0 {
		out.WriteByte('!')
		out.WriteString(nuh.User)
	}
	if len(nuh.Host) != 0 {
		out.WriteByte('@')
		out.WriteString(nuh.Host)
	}
	return out.String()
}