package handler

import (
	"net/http"
	"strings"

	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"

	"learning-service/internal/model"
	"learning-service/internal/repository"
)

type TestHandler struct {
	repo *repository.TestRepository
}

func NewTestHandler(repo *repository.TestRepository) *TestHandler {
	return &TestHandler{repo: repo}
}

// List — GET /tests. Параметры:
//   ?mine=true — только мои (owner_user_id = X-User-Id);
//   без mine — published тесты (для прохождения).
//
// MVP: ещё не подключён access_grants-фильтр; до этого момента «published»
// = «всем видно». Следующая итерация: handler через AccessRepository
// получит visibleIDs и передаст в repo.List.
func (h *TestHandler) List(w http.ResponseWriter, r *http.Request) {
	uid, ok := userIDFromHeader(r)
	if !ok {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}
	mine := r.URL.Query().Get("mine") == "true"
	var ownerFilter *uuid.UUID
	if mine {
		ownerFilter = &uid
	}
	tests, err := h.repo.List(r.Context(), ownerFilter, !mine, nil)
	if err != nil {
		writeRepoError(w, r, err, "list tests")
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"items": tests})
}

func (h *TestHandler) Get(w http.ResponseWriter, r *http.Request) {
	id, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}
	t, err := h.repo.Get(r.Context(), id)
	if err != nil {
		writeRepoError(w, r, err, "get test")
		return
	}
	writeJSON(w, http.StatusOK, t)
}

func (h *TestHandler) Create(w http.ResponseWriter, r *http.Request) {
	uid, ok := userIDFromHeader(r)
	if !ok {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}
	var req model.CreateTestRequest
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid body")
		return
	}
	if strings.TrimSpace(req.Title) == "" {
		writeError(w, http.StatusBadRequest, "title is required")
		return
	}
	t, err := h.repo.Create(r.Context(), uid, req)
	if err != nil {
		writeRepoError(w, r, err, "create test")
		return
	}
	writeJSON(w, http.StatusCreated, t)
}

// Update / Delete: пока без access-проверки (только owner). Когда подключим
// access_grants с can_manage, разрешим co-owner'ам тоже редактировать.
func (h *TestHandler) Update(w http.ResponseWriter, r *http.Request) {
	uid, ok := userIDFromHeader(r)
	if !ok {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}
	id, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}
	existing, err := h.repo.Get(r.Context(), id)
	if err != nil {
		writeRepoError(w, r, err, "get test for update")
		return
	}
	if existing.OwnerUserID != uid {
		writeError(w, http.StatusForbidden, "only owner can edit")
		return
	}
	var req model.UpdateTestRequest
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid body")
		return
	}
	t, err := h.repo.Update(r.Context(), id, req)
	if err != nil {
		writeRepoError(w, r, err, "update test")
		return
	}
	writeJSON(w, http.StatusOK, t)
}

func (h *TestHandler) Delete(w http.ResponseWriter, r *http.Request) {
	uid, ok := userIDFromHeader(r)
	if !ok {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}
	id, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}
	existing, err := h.repo.Get(r.Context(), id)
	if err != nil {
		writeRepoError(w, r, err, "get test for delete")
		return
	}
	if existing.OwnerUserID != uid {
		writeError(w, http.StatusForbidden, "only owner can delete")
		return
	}
	if err := h.repo.Delete(r.Context(), id); err != nil {
		writeRepoError(w, r, err, "delete test")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// ListQuestions — вопросы теста с ответами. Если запросивший не владелец —
// is_correct поле обнуляется в ответе (показывать правильные ответы до
// сабмита нельзя — иначе тест теряет смысл).
func (h *TestHandler) ListQuestions(w http.ResponseWriter, r *http.Request) {
	uid, ok := userIDFromHeader(r)
	if !ok {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}
	testID, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}
	t, err := h.repo.Get(r.Context(), testID)
	if err != nil {
		writeRepoError(w, r, err, "get test")
		return
	}
	qs, err := h.repo.ListQuestions(r.Context(), testID)
	if err != nil {
		writeRepoError(w, r, err, "list questions")
		return
	}
	// Не-владельцу скрываем is_correct, чтобы он не подсмотрел через
	// DevTools правильные ответы до сабмита.
	if t.OwnerUserID != uid {
		for i := range qs {
			for j := range qs[i].Answers {
				qs[i].Answers[j].IsCorrect = false
			}
			// Объяснение тоже не светим — оно потенциально содержит
			// разбор правильного ответа.
			qs[i].Explanation = ""
		}
	}
	writeJSON(w, http.StatusOK, map[string]any{"items": qs})
}

func (h *TestHandler) CreateQuestion(w http.ResponseWriter, r *http.Request) {
	uid, ok := userIDFromHeader(r)
	if !ok {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}
	testID, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}
	t, err := h.repo.Get(r.Context(), testID)
	if err != nil {
		writeRepoError(w, r, err, "get test")
		return
	}
	if t.OwnerUserID != uid {
		writeError(w, http.StatusForbidden, "only owner can add questions")
		return
	}
	var req model.CreateQuestionRequest
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid body")
		return
	}
	if strings.TrimSpace(req.Text) == "" {
		writeError(w, http.StatusBadRequest, "text is required")
		return
	}
	if req.Kind != "single" && req.Kind != "multi" && req.Kind != "text" {
		writeError(w, http.StatusBadRequest, "kind must be single|multi|text")
		return
	}
	if req.Points <= 0 {
		req.Points = 1
	}
	q, err := h.repo.CreateQuestion(r.Context(), testID, req)
	if err != nil {
		writeRepoError(w, r, err, "create question")
		return
	}
	writeJSON(w, http.StatusCreated, q)
}

// UpdateQuestion — PUT /tests/{id}/questions/{questionId}. Full-replace
// семантика (см. repository.UpdateQuestion): метаданные обновляются,
// ответы пересоздаются. question_id стабилен.
func (h *TestHandler) UpdateQuestion(w http.ResponseWriter, r *http.Request) {
	uid, ok := userIDFromHeader(r)
	if !ok {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}
	testID, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid test id")
		return
	}
	qID, err := parseUUID(chi.URLParam(r, "questionId"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid question id")
		return
	}
	t, err := h.repo.Get(r.Context(), testID)
	if err != nil {
		writeRepoError(w, r, err, "get test")
		return
	}
	if t.OwnerUserID != uid {
		writeError(w, http.StatusForbidden, "only owner can edit questions")
		return
	}
	var req model.CreateQuestionRequest
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid body")
		return
	}
	if strings.TrimSpace(req.Text) == "" {
		writeError(w, http.StatusBadRequest, "text is required")
		return
	}
	if req.Kind != "single" && req.Kind != "multi" && req.Kind != "text" {
		writeError(w, http.StatusBadRequest, "kind must be single|multi|text")
		return
	}
	if req.Points <= 0 {
		req.Points = 1
	}
	q, err := h.repo.UpdateQuestion(r.Context(), qID, req)
	if err != nil {
		writeRepoError(w, r, err, "update question")
		return
	}
	writeJSON(w, http.StatusOK, q)
}

// ReorderQuestions — POST /tests/{id}/questions/reorder. Body:
// {"items": [{"id": "uuid", "position": 0}, ...]}
func (h *TestHandler) ReorderQuestions(w http.ResponseWriter, r *http.Request) {
	uid, ok := userIDFromHeader(r)
	if !ok {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}
	testID, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid test id")
		return
	}
	t, err := h.repo.Get(r.Context(), testID)
	if err != nil {
		writeRepoError(w, r, err, "get test")
		return
	}
	if t.OwnerUserID != uid {
		writeError(w, http.StatusForbidden, "only owner can reorder")
		return
	}
	var req struct {
		Items []struct {
			ID       string `json:"id"`
			Position int    `json:"position"`
		} `json:"items"`
	}
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid body")
		return
	}
	items := make([]struct {
		ID       uuid.UUID
		Position int
	}, 0, len(req.Items))
	for _, it := range req.Items {
		id, err := parseUUID(it.ID)
		if err != nil {
			writeError(w, http.StatusBadRequest, "invalid item id")
			return
		}
		items = append(items, struct {
			ID       uuid.UUID
			Position int
		}{ID: id, Position: it.Position})
	}
	if err := h.repo.ReorderQuestions(r.Context(), testID, items); err != nil {
		writeRepoError(w, r, err, "reorder questions")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func (h *TestHandler) DeleteQuestion(w http.ResponseWriter, r *http.Request) {
	uid, ok := userIDFromHeader(r)
	if !ok {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}
	testID, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}
	qID, err := parseUUID(chi.URLParam(r, "questionId"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid question id")
		return
	}
	t, err := h.repo.Get(r.Context(), testID)
	if err != nil {
		writeRepoError(w, r, err, "get test")
		return
	}
	if t.OwnerUserID != uid {
		writeError(w, http.StatusForbidden, "only owner can delete questions")
		return
	}
	if err := h.repo.DeleteQuestion(r.Context(), qID); err != nil {
		writeRepoError(w, r, err, "delete question")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}