package ui

import (
	"fmt"
	"regexp"
	"strings"

	"github.com/ayntgl/discordgo"
)

var (
	boldRegex          = regexp.MustCompile(`(?m)\*\*(.*?)\*\*`)
	italicRegex        = regexp.MustCompile(`(?m)\*(.*?)\*`)
	underlineRegex     = regexp.MustCompile(`(?m)__(.*?)__`)
	strikeThroughRegex = regexp.MustCompile(`(?m)~~(.*?)~~`)
)

func channelToString(c *discordgo.Channel) string {
	var repr string
	if c.Name != "" {
		repr = "#" + c.Name
	} else if len(c.Recipients) == 1 {
		rp := c.Recipients[0]
		repr = rp.Username + "#" + rp.Discriminator
	} else {
		rps := make([]string, len(c.Recipients))
		for i, r := range c.Recipients {
			rps[i] = r.Username + "#" + r.Discriminator
		}

		repr = strings.Join(rps, ", ")
	}

	return repr
}

func hasKeybinding(ks []string, k string) bool {
	for _, repr := range ks {
		if repr == k {
			return true
		}
	}

	return false
}

func buildMessage(app *App, m *discordgo.Message) []byte {
	var b strings.Builder

	switch m.Type {
	case discordgo.MessageTypeDefault, discordgo.MessageTypeReply:
		// Define a new region and assign message ID as the region ID.
		// Learn more:
		// https://pkg.go.dev/github.com/rivo/tview#hdr-Regions_and_Highlights
		b.WriteString("[\"")
		b.WriteString(m.ID)
		b.WriteString("\"]")
		// Build the message associated with crosspost, channel follow add, pin, or a reply.
		buildReferencedMessage(&b, m.ReferencedMessage, app.Session.State.User.ID)
		// Build the author of this message.
		buildAuthor(&b, m.Author, app.Session.State.User.ID)
		// Build the contents of the message.
		buildContent(&b, m, app.Session.State.User.ID)

		if m.EditedTimestamp != "" {
			b.WriteString(" [::d](edited)[::-]")
		}
		// Build the embeds associated with the message.
		buildEmbeds(&b, m.Embeds)
		// Build the message attachments (attached files to the message).
		buildAttachments(&b, m.Attachments)
		// Tags with no region ID ([""]) do not start new regions. They can
		// therefore be used to mark the end of a region.
		b.WriteString("[\"\"]")

		b.WriteByte('\n')
	case discordgo.MessageTypeGuildMemberJoin:
		b.WriteString("[#5865F2]")
		b.WriteString(m.Author.Username)
		b.WriteString("[-] joined the server.")

		b.WriteByte('\n')
	case discordgo.MessageTypeCall:
		b.WriteString("[#5865F2]")
		b.WriteString(m.Author.Username)
		b.WriteString("[-] started a call.")

		b.WriteByte('\n')
	case discordgo.MessageTypeChannelPinnedMessage:
		b.WriteString("[#5865F2]")
		b.WriteString(m.Author.Username)
		b.WriteString("[-] pinned a message.")

		b.WriteByte('\n')
	}

	if str := b.String(); str != "" {
		b := make([]byte, len(str)+1)
		copy(b, str)

		return b
	}

	return nil
}

func buildReferencedMessage(b *strings.Builder, rm *discordgo.Message, clientID string) {
	if rm != nil {
		b.WriteString(" ╭ ")
		b.WriteString("[::d]")
		buildAuthor(b, rm.Author, clientID)

		if rm.Content != "" {
			rm.Content = buildMentions(rm.Content, rm.Mentions, clientID)
			b.WriteString(parseMarkdown(rm.Content))
		}

		b.WriteString("[::-]")
		b.WriteByte('\n')
	}
}

func buildContent(b *strings.Builder, m *discordgo.Message, clientID string) {
	if m.Content != "" {
		m.Content = buildMentions(m.Content, m.Mentions, clientID)
		b.WriteString(parseMarkdown(m.Content))
	}
}

func buildEmbeds(b *strings.Builder, es []*discordgo.MessageEmbed) {
	for _, e := range es {
		if e.Type != discordgo.EmbedTypeRich {
			continue
		}

		var embedBuilder strings.Builder
		var hasHeading bool
		prefix := fmt.Sprintf("[#%06X]▐[-] ", e.Color)

		b.WriteByte('\n')
		embedBuilder.WriteString(prefix)

		if e.Author != nil {
			hasHeading = true
			embedBuilder.WriteString("[::u]")
			embedBuilder.WriteString(e.Author.Name)
			embedBuilder.WriteString("[::-]")
		}

		if e.Title != "" {
			hasHeading = true
			embedBuilder.WriteString("[::b]")
			embedBuilder.WriteString(e.Title)
			embedBuilder.WriteString("[::-]")
		}

		if e.Description != "" {
			if hasHeading {
				embedBuilder.WriteString("\n\n")
			}

			embedBuilder.WriteString(parseMarkdown(e.Description))
		}

		if len(e.Fields) != 0 {
			if hasHeading || e.Description != "" {
				embedBuilder.WriteString("\n\n")
			}

			for i, ef := range e.Fields {
				embedBuilder.WriteString("[::b]")
				embedBuilder.WriteString(ef.Name)
				embedBuilder.WriteString("[::-]")
				embedBuilder.WriteByte('\n')
				embedBuilder.WriteString(parseMarkdown(ef.Value))

				if i != len(e.Fields)-1 {
					embedBuilder.WriteString("\n\n")
				}
			}
		}

		if e.Footer != nil {
			if hasHeading {
				embedBuilder.WriteString("\n\n")
			}

			embedBuilder.WriteString(e.Footer.Text)
		}

		b.WriteString(strings.Replace(embedBuilder.String(), "\n", "\n"+prefix, -1))
	}
}

func buildAttachments(b *strings.Builder, as []*discordgo.MessageAttachment) {
	for _, a := range as {
		b.WriteByte('\n')
		b.WriteByte('[')
		b.WriteString(a.Filename)
		b.WriteString("]: ")
		b.WriteString(a.URL)
	}
}

func buildMentions(content string, mentions []*discordgo.User, clientID string) string {
	for _, mUser := range mentions {
		var color string
		if mUser.ID == clientID {
			color = "[:#5865F2]"
		} else {
			color = "[#EB459E]"
		}

		content = strings.NewReplacer(
			// <@USER_ID>
			"<@"+mUser.ID+">",
			color+"@"+mUser.Username+"[-:-]",
			// <@!USER_ID>
			"<@!"+mUser.ID+">",
			color+"@"+mUser.Username+"[-:-]",
		).Replace(content)
	}

	return content
}

func buildAuthor(b *strings.Builder, u *discordgo.User, clientID string) {
	if u.ID == clientID {
		b.WriteString("[#57F287]")
	} else {
		b.WriteString("[#ED4245]")
	}

	b.WriteString(u.Username)
	b.WriteString("[-] ")
	// If the message author is a bot account, render the message with bot label
	// for distinction.
	if u.Bot {
		b.WriteString("[#EB459E]BOT[-] ")
	}
}

func parseMarkdown(md string) string {
	var res string
	res = boldRegex.ReplaceAllString(md, "[::b]$1[::-]")
	res = italicRegex.ReplaceAllString(res, "[::i]$1[::-]")
	res = underlineRegex.ReplaceAllString(res, "[::u]$1[::-]")
	res = strikeThroughRegex.ReplaceAllString(res, "[::s]$1[::-]")

	return res
}