package handlers

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
	"time"

	"git.eeqj.de/sneak/neoirc/internal/db"
	"git.eeqj.de/sneak/neoirc/pkg/irc"
)

// maxUserhostNicks is the maximum number of nicks allowed
// in a single USERHOST query (RFC 2812).
const maxUserhostNicks = 5

// dispatchBodyOnlyCommand routes commands that take
// (writer, request, sessionID, clientID, nick, bodyLines).
func (hdlr *Handlers) dispatchBodyOnlyCommand(
	writer http.ResponseWriter,
	request *http.Request,
	sessionID, clientID int64,
	nick, command string,
	bodyLines func() []string,
) {
	switch command {
	case irc.CmdAway:
		hdlr.handleAway(
			writer, request,
			sessionID, clientID, nick, bodyLines,
		)
	case irc.CmdNick:
		hdlr.handleNick(
			writer, request,
			sessionID, clientID, nick, bodyLines,
		)
	case irc.CmdPass:
		hdlr.handlePass(
			writer, request,
			sessionID, clientID, nick, bodyLines,
		)
	case irc.CmdInvite:
		hdlr.handleInvite(
			writer, request,
			sessionID, clientID, nick, bodyLines,
		)
	}
}

// dispatchOperCommand routes oper-related commands (OPER,
// KILL, WALLOPS) to their handlers.
func (hdlr *Handlers) dispatchOperCommand(
	writer http.ResponseWriter,
	request *http.Request,
	sessionID, clientID int64,
	nick, command string,
	bodyLines func() []string,
) {
	switch command {
	case irc.CmdOper:
		hdlr.handleOper(
			writer, request,
			sessionID, clientID, nick, bodyLines,
		)
	case irc.CmdKill:
		hdlr.handleKill(
			writer, request,
			sessionID, clientID, nick, bodyLines,
		)
	case irc.CmdWallops:
		hdlr.handleWallops(
			writer, request,
			sessionID, clientID, nick, bodyLines,
		)
	}
}

// handleUserhost handles the USERHOST command.
// Returns user@host info for up to 5 nicks.
func (hdlr *Handlers) handleUserhost(
	writer http.ResponseWriter,
	request *http.Request,
	sessionID, clientID int64,
	nick string,
	bodyLines func() []string,
) {
	ctx := request.Context()

	lines := bodyLines()
	if len(lines) == 0 {
		hdlr.respondIRCError(
			writer, request, clientID, sessionID,
			irc.ErrNeedMoreParams, nick,
			[]string{irc.CmdUserhost},
			"Not enough parameters",
		)

		return
	}

	// Limit to 5 nicks per RFC 2812.
	nicks := lines
	if len(nicks) > maxUserhostNicks {
		nicks = nicks[:maxUserhostNicks]
	}

	infos, err := hdlr.params.Database.GetUserhostInfo(
		ctx, nicks,
	)
	if err != nil {
		hdlr.log.Error(
			"userhost query failed", "error", err,
		)
		hdlr.respondError(
			writer, request,
			"internal error",
			http.StatusInternalServerError,
		)

		return
	}

	replyStr := hdlr.buildUserhostReply(infos)

	hdlr.enqueueNumeric(
		ctx, clientID, irc.RplUserHost, nick, nil,
		replyStr,
	)

	hdlr.broker.Notify(sessionID)
	hdlr.respondJSON(writer, request,
		map[string]string{"status": "ok"},
		http.StatusOK)
}

// buildUserhostReply builds the RPL_USERHOST reply
// string per RFC 2812.
func (hdlr *Handlers) buildUserhostReply(
	infos []db.UserhostInfo,
) string {
	replies := make([]string, 0, len(infos))

	for idx := range infos {
		info := &infos[idx]

		username := info.Username
		if username == "" {
			username = info.Nick
		}

		hostname := info.Hostname
		if hostname == "" {
			hostname = hdlr.serverName()
		}

		operStar := ""
		if info.IsOper {
			operStar = "*"
		}

		awayPrefix := "+"
		if info.AwayMessage != "" {
			awayPrefix = "-"
		}

		replies = append(replies,
			info.Nick+operStar+"="+
				awayPrefix+username+"@"+hostname,
		)
	}

	return strings.Join(replies, " ")
}

// handleVersion handles the VERSION command.
// Returns the server version string.
func (hdlr *Handlers) handleVersion(
	writer http.ResponseWriter,
	request *http.Request,
	sessionID, clientID int64,
	nick string,
) {
	ctx := request.Context()
	srvName := hdlr.serverName()
	version := hdlr.serverVersion()

	// 351 RPL_VERSION
	hdlr.enqueueNumeric(
		ctx, clientID, irc.RplVersion, nick,
		[]string{version + ".", srvName},
		"",
	)

	hdlr.broker.Notify(sessionID)
	hdlr.respondJSON(writer, request,
		map[string]string{"status": "ok"},
		http.StatusOK)
}

// handleAdmin handles the ADMIN command.
// Returns server admin contact info.
func (hdlr *Handlers) handleAdmin(
	writer http.ResponseWriter,
	request *http.Request,
	sessionID, clientID int64,
	nick string,
) {
	ctx := request.Context()
	srvName := hdlr.serverName()

	// 256 RPL_ADMINME
	hdlr.enqueueNumeric(
		ctx, clientID, irc.RplAdminMe, nick,
		[]string{srvName},
		"Administrative info",
	)

	// 257 RPL_ADMINLOC1
	hdlr.enqueueNumeric(
		ctx, clientID, irc.RplAdminLoc1, nick, nil,
		"neoirc server",
	)

	// 258 RPL_ADMINLOC2
	hdlr.enqueueNumeric(
		ctx, clientID, irc.RplAdminLoc2, nick, nil,
		"IRC over HTTP",
	)

	// 259 RPL_ADMINEMAIL
	hdlr.enqueueNumeric(
		ctx, clientID, irc.RplAdminEmail, nick, nil,
		"admin@"+srvName,
	)

	hdlr.broker.Notify(sessionID)
	hdlr.respondJSON(writer, request,
		map[string]string{"status": "ok"},
		http.StatusOK)
}

// handleInfo handles the INFO command.
// Returns server software information.
func (hdlr *Handlers) handleInfo(
	writer http.ResponseWriter,
	request *http.Request,
	sessionID, clientID int64,
	nick string,
) {
	ctx := request.Context()
	version := hdlr.serverVersion()

	infoLines := []string{
		"neoirc — IRC semantics over HTTP",
		"Version: " + version,
		"Written in Go",
		"Started: " +
			hdlr.params.Globals.StartTime.
				Format(time.RFC1123),
	}

	for _, line := range infoLines {
		// 371 RPL_INFO
		hdlr.enqueueNumeric(
			ctx, clientID, irc.RplInfo, nick, nil,
			line,
		)
	}

	// 374 RPL_ENDOFINFO
	hdlr.enqueueNumeric(
		ctx, clientID, irc.RplEndOfInfo, nick, nil,
		"End of /INFO list",
	)

	hdlr.broker.Notify(sessionID)
	hdlr.respondJSON(writer, request,
		map[string]string{"status": "ok"},
		http.StatusOK)
}

// handleTime handles the TIME command.
// Returns the server's local time in RFC format.
func (hdlr *Handlers) handleTime(
	writer http.ResponseWriter,
	request *http.Request,
	sessionID, clientID int64,
	nick string,
) {
	ctx := request.Context()
	srvName := hdlr.serverName()

	// 391 RPL_TIME
	hdlr.enqueueNumeric(
		ctx, clientID, irc.RplTime, nick,
		[]string{srvName},
		time.Now().Format(time.RFC1123),
	)

	hdlr.broker.Notify(sessionID)
	hdlr.respondJSON(writer, request,
		map[string]string{"status": "ok"},
		http.StatusOK)
}

// handleKill handles the KILL command.
// Forcibly disconnects a user (oper only).
func (hdlr *Handlers) handleKill(
	writer http.ResponseWriter,
	request *http.Request,
	sessionID, clientID int64,
	nick string,
	bodyLines func() []string,
) {
	ctx := request.Context()

	// Check oper status.
	isOper, err := hdlr.params.Database.IsSessionOper(
		ctx, sessionID,
	)
	if err != nil || !isOper {
		hdlr.respondIRCError(
			writer, request, clientID, sessionID,
			irc.ErrNoPrivileges, nick, nil,
			"Permission Denied- You're not an IRC operator",
		)

		return
	}

	lines := bodyLines()
	if len(lines) == 0 {
		hdlr.respondIRCError(
			writer, request, clientID, sessionID,
			irc.ErrNeedMoreParams, nick,
			[]string{irc.CmdKill},
			"Not enough parameters",
		)

		return
	}

	targetNick := strings.TrimSpace(lines[0])
	if targetNick == "" {
		hdlr.respondIRCError(
			writer, request, clientID, sessionID,
			irc.ErrNeedMoreParams, nick,
			[]string{irc.CmdKill},
			"Not enough parameters",
		)

		return
	}

	reason := "KILLed"
	if len(lines) > 1 {
		reason = lines[1]
	}

	targetSID, lookupErr := hdlr.params.Database.
		GetSessionByNick(ctx, targetNick)
	if lookupErr != nil {
		hdlr.respondIRCError(
			writer, request, clientID, sessionID,
			irc.ErrNoSuchNick, nick,
			[]string{targetNick},
			"No such nick/channel",
		)

		return
	}

	// Do not allow killing yourself.
	if targetSID == sessionID {
		hdlr.respondIRCError(
			writer, request, clientID, sessionID,
			irc.ErrCantKillServer, nick, nil,
			"You cannot KILL yourself",
		)

		return
	}

	hdlr.executeKillUser(
		request, targetSID, targetNick, nick, reason,
	)

	hdlr.respondJSON(writer, request,
		map[string]string{"status": "ok"},
		http.StatusOK)
}

// executeKillUser forcibly disconnects a user: broadcasts
// QUIT to their channels, parts all channels, and deletes
// the session.
func (hdlr *Handlers) executeKillUser(
	request *http.Request,
	targetSID int64,
	targetNick, killerNick, reason string,
) {
	ctx := request.Context()

	quitMsg := "Killed (" + killerNick + " (" + reason + "))"

	quitBody, err := json.Marshal([]string{quitMsg})
	if err != nil {
		hdlr.log.Error(
			"marshal kill quit body", "error", err,
		)

		return
	}

	channels, _ := hdlr.params.Database.
		GetSessionChannels(ctx, targetSID)

	notified := map[int64]bool{}

	var dbID int64

	if len(channels) > 0 {
		dbID, _, _ = hdlr.params.Database.InsertMessage(
			ctx, irc.CmdQuit, targetNick, "",
			nil, json.RawMessage(quitBody), nil,
		)
	}

	for _, chanInfo := range channels {
		memberIDs, _ := hdlr.params.Database.
			GetChannelMemberIDs(ctx, chanInfo.ID)

		for _, mid := range memberIDs {
			if mid != targetSID && !notified[mid] {
				notified[mid] = true

				_ = hdlr.params.Database.EnqueueToSession(
					ctx, mid, dbID,
				)

				hdlr.broker.Notify(mid)
			}
		}

		_ = hdlr.params.Database.PartChannel(
			ctx, chanInfo.ID, targetSID,
		)

		_ = hdlr.params.Database.DeleteChannelIfEmpty(
			ctx, chanInfo.ID,
		)
	}

	_ = hdlr.params.Database.DeleteSession(
		ctx, targetSID,
	)
}

// handleWallops handles the WALLOPS command.
// Broadcasts a message to all users with +w usermode
// (oper only).
func (hdlr *Handlers) handleWallops(
	writer http.ResponseWriter,
	request *http.Request,
	sessionID, clientID int64,
	nick string,
	bodyLines func() []string,
) {
	ctx := request.Context()

	// Check oper status.
	isOper, err := hdlr.params.Database.IsSessionOper(
		ctx, sessionID,
	)
	if err != nil || !isOper {
		hdlr.respondIRCError(
			writer, request, clientID, sessionID,
			irc.ErrNoPrivileges, nick, nil,
			"Permission Denied- You're not an IRC operator",
		)

		return
	}

	lines := bodyLines()
	if len(lines) == 0 {
		hdlr.respondIRCError(
			writer, request, clientID, sessionID,
			irc.ErrNeedMoreParams, nick,
			[]string{irc.CmdWallops},
			"Not enough parameters",
		)

		return
	}

	message := strings.Join(lines, " ")

	wallopsSIDs, err := hdlr.params.Database.
		GetWallopsSessionIDs(ctx)
	if err != nil {
		hdlr.log.Error(
			"get wallops sessions failed", "error", err,
		)
		hdlr.respondError(
			writer, request,
			"internal error",
			http.StatusInternalServerError,
		)

		return
	}

	if len(wallopsSIDs) > 0 {
		body, mErr := json.Marshal([]string{message})
		if mErr != nil {
			hdlr.log.Error(
				"marshal wallops body", "error", mErr,
			)
			hdlr.respondError(
				writer, request,
				"internal error",
				http.StatusInternalServerError,
			)

			return
		}

		_ = hdlr.fanOutSilent(
			request, irc.CmdWallops, nick, "*",
			json.RawMessage(body), wallopsSIDs,
		)
	}

	hdlr.respondJSON(writer, request,
		map[string]string{"status": "ok"},
		http.StatusOK)
}

// handleUserMode handles user mode queries and changes
// (e.g., MODE nick, MODE nick +w).
func (hdlr *Handlers) handleUserMode(
	writer http.ResponseWriter,
	request *http.Request,
	sessionID, clientID int64,
	nick, target string,
	bodyLines func() []string,
) {
	ctx := request.Context()

	lines := bodyLines()

	// Mode change requested.
	if len(lines) > 0 {
		// Users can only change their own modes.
		if target != nick && target != "" {
			hdlr.respondIRCError(
				writer, request, clientID, sessionID,
				irc.ErrUsersDoNotMatch, nick, nil,
				"Can't change mode for other users",
			)

			return
		}

		hdlr.applyUserModeChange(
			writer, request,
			sessionID, clientID, nick, lines[0],
		)

		return
	}

	// Mode query — build the current mode string.
	modeStr := hdlr.buildUserModeString(ctx, sessionID)

	hdlr.enqueueNumeric(
		ctx, clientID, irc.RplUmodeIs, nick, nil,
		modeStr,
	)
	hdlr.broker.Notify(sessionID)
	hdlr.respondJSON(writer, request,
		map[string]string{"status": "ok"},
		http.StatusOK)
}

// buildUserModeString constructs the mode string for a
// user (e.g., "+ow" for oper+wallops).
func (hdlr *Handlers) buildUserModeString(
	ctx context.Context,
	sessionID int64,
) string {
	modes := "+"

	isOper, err := hdlr.params.Database.IsSessionOper(
		ctx, sessionID,
	)
	if err == nil && isOper {
		modes += "o"
	}

	isWallops, err := hdlr.params.Database.IsSessionWallops(
		ctx, sessionID,
	)
	if err == nil && isWallops {
		modes += "w"
	}

	return modes
}

// applyUserModeChange applies a user mode change string
// (e.g., "+w", "-w").
func (hdlr *Handlers) applyUserModeChange(
	writer http.ResponseWriter,
	request *http.Request,
	sessionID, clientID int64,
	nick, modeStr string,
) {
	ctx := request.Context()

	if len(modeStr) < 2 { //nolint:mnd // +/- and mode char
		hdlr.respondIRCError(
			writer, request, clientID, sessionID,
			irc.ErrUmodeUnknownFlag, nick, nil,
			"Unknown MODE flag",
		)

		return
	}

	adding := modeStr[0] == '+'
	modeChar := modeStr[1:]

	applied, err := hdlr.applyModeChar(
		ctx, writer, request,
		sessionID, clientID, nick,
		modeChar, adding,
	)
	if err != nil || !applied {
		return
	}

	newModes := hdlr.buildUserModeString(ctx, sessionID)

	hdlr.enqueueNumeric(
		ctx, clientID, irc.RplUmodeIs, nick, nil,
		newModes,
	)

	hdlr.broker.Notify(sessionID)
	hdlr.respondJSON(writer, request,
		map[string]string{"status": "ok"},
		http.StatusOK)
}

// applyModeChar applies a single user mode character.
// Returns (applied, error).
func (hdlr *Handlers) applyModeChar(
	ctx context.Context,
	writer http.ResponseWriter,
	request *http.Request,
	sessionID, clientID int64,
	nick, modeChar string,
	adding bool,
) (bool, error) {
	switch modeChar {
	case "w":
		err := hdlr.params.Database.SetSessionWallops(
			ctx, sessionID, adding,
		)
		if err != nil {
			hdlr.log.Error(
				"set wallops mode failed", "error", err,
			)
			hdlr.respondError(
				writer, request,
				"internal error",
				http.StatusInternalServerError,
			)

			return false, fmt.Errorf(
				"set wallops: %w", err,
			)
		}
	case "o":
		// +o cannot be set via MODE, only via OPER.
		if adding {
			hdlr.respondIRCError(
				writer, request, clientID, sessionID,
				irc.ErrUmodeUnknownFlag, nick, nil,
				"Unknown MODE flag",
			)

			return false, nil
		}

		err := hdlr.params.Database.SetSessionOper(
			ctx, sessionID, false,
		)
		if err != nil {
			hdlr.log.Error(
				"clear oper mode failed", "error", err,
			)
			hdlr.respondError(
				writer, request,
				"internal error",
				http.StatusInternalServerError,
			)

			return false, fmt.Errorf(
				"clear oper: %w", err,
			)
		}
	default:
		hdlr.respondIRCError(
			writer, request, clientID, sessionID,
			irc.ErrUmodeUnknownFlag, nick, nil,
			"Unknown MODE flag",
		)

		return false, nil
	}

	return true, nil
}