package server

import (
	"net/http"
	"slices"

	"github.com/gin-gonic/gin"
	"github.com/google/uuid"

	"scrabble/backend/internal/engine"
	"scrabble/backend/internal/gamelimits"
)

// The /api/v1/user/* endpoints require X-User-ID (RequireUserID middleware). The
// backend treats that header as the sole identity input.

// handleProfile returns the authenticated account's own profile.
func (s *Server) handleProfile(c *gin.Context) {
	uid, ok := userID(c)
	if !ok {
		abortBadRequest(c, "missing identity")
		return
	}
	acc, err := s.accounts.GetByID(c.Request.Context(), uid)
	if err != nil {
		s.abortErr(c, err)
		return
	}
	// The SPA fetches the profile once per cold app-load, so stamp the account's last
	// login time and client IP here (throttled to at most once an hour). Best-effort: it
	// feeds the deletion dossier, never blocks the profile read.
	_ = s.accounts.StampLastLogin(c.Request.Context(), uid, clientIP(c))
	c.JSON(http.StatusOK, s.profileResponse(c.Request.Context(), acc))
}

// submitPlayRequest places tiles on the player's turn; the engine infers the
// play's orientation from the tiles and the board. Each tile's Letter is a wire
// alphabet index; for a blank it is the designated letter's index.
type submitPlayRequest struct {
	Tiles []struct {
		Row    int  `json:"row"`
		Col    int  `json:"col"`
		Letter int  `json:"letter"`
		Blank  bool `json:"blank"`
	} `json:"tiles"`
}

// tilesFromRequest maps a play/evaluate request's index-addressed tiles to engine tile
// records for the game's variant (a placed blank carries its designated letter's
// index with Blank set). An out-of-range index surfaces as engine.ErrIllegalPlay (HTTP 400).
func tilesFromRequest(variant engine.Variant, req submitPlayRequest) ([]engine.TileRecord, error) {
	tiles := make([]engine.TileRecord, 0, len(req.Tiles))
	for _, t := range req.Tiles {
		letter, err := engine.LetterForIndex(variant, t.Letter)
		if err != nil {
			return nil, err
		}
		tiles = append(tiles, engine.TileRecord{Row: t.Row, Col: t.Col, Letter: letter, Blank: t.Blank})
	}
	return tiles, nil
}

// handleSubmitPlay validates, scores and commits a placement.
func (s *Server) handleSubmitPlay(c *gin.Context) {
	uid, ok := userID(c)
	if !ok {
		abortBadRequest(c, "missing identity")
		return
	}
	gameID, ok := gameIDParam(c)
	if !ok {
		abortBadRequest(c, "invalid game id")
		return
	}
	var req submitPlayRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		abortBadRequest(c, "invalid request body")
		return
	}
	variant, err := s.games.GameVariant(c.Request.Context(), gameID)
	if err != nil {
		s.abortErr(c, err)
		return
	}
	tiles, err := tilesFromRequest(variant, req)
	if err != nil {
		s.abortErr(c, err)
		return
	}
	res, err := s.games.SubmitPlay(c.Request.Context(), gameID, uid, tiles)
	if err != nil {
		s.abortErr(c, err)
		return
	}
	s.writeMoveResult(c, res)
}

// handleGameState returns the player's view of a game.
// handleHideGame hides a finished game from the caller's own lobby list.
func (s *Server) handleHideGame(c *gin.Context) {
	uid, ok := userID(c)
	if !ok {
		abortBadRequest(c, "missing identity")
		return
	}
	gameID, ok := gameIDParam(c)
	if !ok {
		abortBadRequest(c, "invalid game id")
		return
	}
	if err := s.games.HideGame(c.Request.Context(), uid, gameID); err != nil {
		s.abortErr(c, err)
		return
	}
	c.JSON(http.StatusOK, okResponse{OK: true})
}

func (s *Server) handleGameState(c *gin.Context) {
	uid, ok := userID(c)
	if !ok {
		abortBadRequest(c, "missing identity")
		return
	}
	gameID, ok := gameIDParam(c)
	if !ok {
		abortBadRequest(c, "invalid game id")
		return
	}
	view, err := s.games.GameState(c.Request.Context(), gameID, uid)
	if err != nil {
		s.abortErr(c, err)
		return
	}
	dto, err := stateDTOFrom(view, c.Query("include_alphabet") == "true")
	if err != nil {
		s.abortErr(c, err)
		return
	}
	s.fillSeatNames(c.Request.Context(), &dto.Game, map[string]string{})
	s.setUnreadChat(c.Request.Context(), &dto.Game, uid)
	c.JSON(http.StatusOK, dto)
}

// ensureVariantAllowed reports whether the caller's profile permits creating a game
// of variant — it must be one of their VariantPreferences. It aborts the request
// with 400 and returns false otherwise. Only the player who creates a game (quick
// match, vs-AI or a friend invitation) is gated this way; an invited friend may
// accept an invitation in any variant.
func (s *Server) ensureVariantAllowed(c *gin.Context, uid uuid.UUID, variant string) bool {
	acc, err := s.accounts.GetByID(c.Request.Context(), uid)
	if err != nil {
		s.abortErr(c, err)
		return false
	}
	if !slices.Contains(acc.VariantPreferences, variant) {
		abortBadRequest(c, "variant is not in your preferences")
		return false
	}
	return true
}

// enqueueRequest enters per-variant auto-match under a per-turn word rule. VsAI true
// starts an honest-AI game against a robot instead of the open/wait matchmaking path.
type enqueueRequest struct {
	Variant              string `json:"variant"`
	MultipleWordsPerTurn bool   `json:"multiple_words_per_turn"`
	VsAI                 bool   `json:"vs_ai"`
}

// handleEnqueue enters the caller into a quick game and returns the game they land in
// immediately. With vs_ai it starts an honest-AI game already seated with a robot;
// otherwise it enters auto-match — a freshly opened game awaiting an opponent, or
// another player's open game they just joined. The client navigates straight in.
func (s *Server) handleEnqueue(c *gin.Context) {
	uid, ok := userID(c)
	if !ok {
		abortBadRequest(c, "missing identity")
		return
	}
	var req enqueueRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		abortBadRequest(c, "invalid request body")
		return
	}
	variant, err := engine.ParseVariant(req.Variant)
	if err != nil {
		abortBadRequest(c, "unknown variant")
		return
	}
	if !s.ensureVariantAllowed(c, uid, variant.String()) {
		return
	}
	kind := gamelimits.KindRandom
	enter := s.matchmaker.Enqueue
	if req.VsAI {
		kind = gamelimits.KindVsAI
		enter = s.matchmaker.StartVsAI
	}
	if !s.ensureUnderGameLimit(c, uid, kind) {
		return
	}
	res, err := enter(c.Request.Context(), uid, variant, req.MultipleWordsPerTurn)
	if err != nil {
		s.abortErr(c, err)
		return
	}
	dto := matchDTOFrom(res)
	if dto.Game != nil {
		s.fillSeatNames(c.Request.Context(), dto.Game, map[string]string{})
	}
	c.JSON(http.StatusOK, dto)
}

// chatPostRequest posts a per-game chat message.
type chatPostRequest struct {
	Body string `json:"body"`
}

// handleChatPost stores a chat message from the authenticated player. The sender
// IP is taken from the gateway-forwarded X-Forwarded-For header.
func (s *Server) handleChatPost(c *gin.Context) {
	uid, ok := userID(c)
	if !ok {
		abortBadRequest(c, "missing identity")
		return
	}
	gameID, ok := gameIDParam(c)
	if !ok {
		abortBadRequest(c, "invalid game id")
		return
	}
	var req chatPostRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		abortBadRequest(c, "invalid request body")
		return
	}
	msg, err := s.social.PostMessage(c.Request.Context(), gameID, uid, req.Body, clientIP(c))
	if err != nil {
		s.abortErr(c, err)
		return
	}
	c.JSON(http.StatusOK, chatDTOFrom(msg))
}