package api

import (
	"encoding/json"
	"net/http"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"
	"github.com/shopspring/decimal"
	"simplefinancedash/backend/internal/auth"
	"simplefinancedash/backend/internal/db"
	"simplefinancedash/backend/internal/models"
)

type Handlers struct {
	queries       *db.Queries
	sessionSecret string
}

func NewHandlers(queries *db.Queries, sessionSecret string) *Handlers {
	return &Handlers{queries: queries, sessionSecret: sessionSecret}
}

// Helpers

func writeJSON(w http.ResponseWriter, status int, v interface{}) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(v)
}

func writeError(w http.ResponseWriter, status int, msg string) {
	writeJSON(w, status, map[string]string{"error": msg})
}

func decodeJSON(r *http.Request, v interface{}) error {
	return json.NewDecoder(r.Body).Decode(v)
}

func parseUUID(s string) (uuid.UUID, error) {
	return uuid.Parse(s)
}

// Auth Handlers

func (h *Handlers) Register(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Email       string `json:"email"`
		Password    string `json:"password"`
		DisplayName string `json:"display_name"`
	}
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	if req.Email == "" || req.Password == "" {
		writeError(w, http.StatusBadRequest, "email and password required")
		return
	}

	hash, err := auth.HashPassword(req.Password)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "internal error")
		return
	}

	user, err := h.queries.CreateUser(r.Context(), req.Email, hash, req.DisplayName, "en")
	if err != nil {
		writeError(w, http.StatusConflict, "email already registered")
		return
	}

	token, err := auth.GenerateToken(user.ID, h.sessionSecret)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "internal error")
		return
	}

	auth.SetSessionCookie(w, token)
	writeJSON(w, http.StatusCreated, user)
}

func (h *Handlers) Login(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Email    string `json:"email"`
		Password string `json:"password"`
	}
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	user, err := h.queries.GetUserByEmail(r.Context(), req.Email)
	if err != nil {
		writeError(w, http.StatusUnauthorized, "invalid credentials")
		return
	}

	if err := auth.CheckPassword(user.PasswordHash, req.Password); err != nil {
		writeError(w, http.StatusUnauthorized, "invalid credentials")
		return
	}

	token, err := auth.GenerateToken(user.ID, h.sessionSecret)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "internal error")
		return
	}

	auth.SetSessionCookie(w, token)
	writeJSON(w, http.StatusOK, user)
}

func (h *Handlers) Logout(w http.ResponseWriter, r *http.Request) {
	auth.ClearSessionCookie(w)
	w.WriteHeader(http.StatusNoContent)
}

func (h *Handlers) Me(w http.ResponseWriter, r *http.Request) {
	cookie, err := r.Cookie("session")
	if err != nil {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}

	userID, err := auth.ValidateToken(cookie.Value, h.sessionSecret)
	if err != nil {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}

	user, err := h.queries.GetUserByID(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}

	writeJSON(w, http.StatusOK, user)
}

func (h *Handlers) OIDCStart(w http.ResponseWriter, r *http.Request) {
	// OIDC flow placeholder - would redirect to OIDC provider
	writeError(w, http.StatusNotImplemented, "OIDC not configured")
}

func (h *Handlers) OIDCCallback(w http.ResponseWriter, r *http.Request) {
	// OIDC callback placeholder
	writeError(w, http.StatusNotImplemented, "OIDC not configured")
}

// Category Handlers

func (h *Handlers) ListCategories(w http.ResponseWriter, r *http.Request) {
	userID := auth.UserIDFromContext(r.Context())
	cats, err := h.queries.ListCategories(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to list categories")
		return
	}
	if cats == nil {
		cats = []models.Category{}
	}
	writeJSON(w, http.StatusOK, cats)
}

func (h *Handlers) CreateCategory(w http.ResponseWriter, r *http.Request) {
	userID := auth.UserIDFromContext(r.Context())
	var req struct {
		Name      string              `json:"name"`
		Type      models.CategoryType `json:"type"`
		Icon      string              `json:"icon"`
		SortOrder int                 `json:"sort_order"`
	}
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	cat, err := h.queries.CreateCategory(r.Context(), userID, req.Name, req.Type, req.Icon, req.SortOrder)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to create category")
		return
	}
	writeJSON(w, http.StatusCreated, cat)
}

func (h *Handlers) UpdateCategory(w http.ResponseWriter, r *http.Request) {
	userID := auth.UserIDFromContext(r.Context())
	id, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}

	var req struct {
		Name      string              `json:"name"`
		Type      models.CategoryType `json:"type"`
		Icon      string              `json:"icon"`
		SortOrder int                 `json:"sort_order"`
	}
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	cat, err := h.queries.UpdateCategory(r.Context(), id, userID, req.Name, req.Type, req.Icon, req.SortOrder)
	if err != nil {
		writeError(w, http.StatusNotFound, "category not found")
		return
	}
	writeJSON(w, http.StatusOK, cat)
}

func (h *Handlers) DeleteCategory(w http.ResponseWriter, r *http.Request) {
	userID := auth.UserIDFromContext(r.Context())
	id, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}

	if err := h.queries.DeleteCategory(r.Context(), id, userID); err != nil {
		writeError(w, http.StatusInternalServerError, "failed to delete category")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// Budget Handlers

func (h *Handlers) ListBudgets(w http.ResponseWriter, r *http.Request) {
	userID := auth.UserIDFromContext(r.Context())
	budgets, err := h.queries.ListBudgets(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to list budgets")
		return
	}
	if budgets == nil {
		budgets = []models.Budget{}
	}
	writeJSON(w, http.StatusOK, budgets)
}

func (h *Handlers) CreateBudget(w http.ResponseWriter, r *http.Request) {
	userID := auth.UserIDFromContext(r.Context())
	var req struct {
		Name            string          `json:"name"`
		StartDate       string          `json:"start_date"`
		EndDate         string          `json:"end_date"`
		Currency        string          `json:"currency"`
		CarryoverAmount decimal.Decimal `json:"carryover_amount"`
	}
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	startDate, err := time.Parse("2006-01-02", req.StartDate)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid start_date format")
		return
	}
	endDate, err := time.Parse("2006-01-02", req.EndDate)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid end_date format")
		return
	}

	if req.Currency == "" {
		req.Currency = "EUR"
	}

	budget, err := h.queries.CreateBudget(r.Context(), userID, req.Name, startDate, endDate, req.Currency, req.CarryoverAmount)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to create budget")
		return
	}
	writeJSON(w, http.StatusCreated, budget)
}

func (h *Handlers) GetBudget(w http.ResponseWriter, r *http.Request) {
	userID := auth.UserIDFromContext(r.Context())
	id, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}

	detail, err := h.queries.GetBudgetWithItems(r.Context(), id, userID)
	if err != nil {
		writeError(w, http.StatusNotFound, "budget not found")
		return
	}
	if detail.Items == nil {
		detail.Items = []models.BudgetItem{}
	}
	writeJSON(w, http.StatusOK, detail)
}

func (h *Handlers) UpdateBudget(w http.ResponseWriter, r *http.Request) {
	userID := auth.UserIDFromContext(r.Context())
	id, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}

	var req struct {
		Name            string          `json:"name"`
		StartDate       string          `json:"start_date"`
		EndDate         string          `json:"end_date"`
		Currency        string          `json:"currency"`
		CarryoverAmount decimal.Decimal `json:"carryover_amount"`
	}
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	startDate, _ := time.Parse("2006-01-02", req.StartDate)
	endDate, _ := time.Parse("2006-01-02", req.EndDate)

	budget, err := h.queries.UpdateBudget(r.Context(), id, userID, req.Name, startDate, endDate, req.Currency, req.CarryoverAmount)
	if err != nil {
		writeError(w, http.StatusNotFound, "budget not found")
		return
	}
	writeJSON(w, http.StatusOK, budget)
}

func (h *Handlers) DeleteBudget(w http.ResponseWriter, r *http.Request) {
	userID := auth.UserIDFromContext(r.Context())
	id, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}

	if err := h.queries.DeleteBudget(r.Context(), id, userID); err != nil {
		writeError(w, http.StatusInternalServerError, "failed to delete budget")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func (h *Handlers) CopyBudgetItems(w http.ResponseWriter, r *http.Request) {
	userID := auth.UserIDFromContext(r.Context())
	id, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}
	srcID, err := parseUUID(chi.URLParam(r, "srcId"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid source id")
		return
	}

	if err := h.queries.CopyBudgetItems(r.Context(), id, srcID, userID); err != nil {
		writeError(w, http.StatusInternalServerError, "failed to copy items")
		return
	}

	detail, err := h.queries.GetBudgetWithItems(r.Context(), id, userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to get budget")
		return
	}
	writeJSON(w, http.StatusOK, detail)
}

// Budget Item Handlers

func (h *Handlers) CreateBudgetItem(w http.ResponseWriter, r *http.Request) {
	budgetID, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid budget id")
		return
	}

	var req struct {
		CategoryID     uuid.UUID       `json:"category_id"`
		BudgetedAmount decimal.Decimal `json:"budgeted_amount"`
		ActualAmount   decimal.Decimal `json:"actual_amount"`
		Notes          string          `json:"notes"`
		ItemTier       models.ItemTier `json:"item_tier"`
	}
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	item, err := h.queries.CreateBudgetItem(r.Context(), budgetID, req.CategoryID, req.BudgetedAmount, req.ActualAmount, req.Notes, req.ItemTier)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to create budget item")
		return
	}
	writeJSON(w, http.StatusCreated, item)
}

func (h *Handlers) UpdateBudgetItem(w http.ResponseWriter, r *http.Request) {
	budgetID, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid budget id")
		return
	}
	itemID, err := parseUUID(chi.URLParam(r, "itemId"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid item id")
		return
	}

	var req struct {
		BudgetedAmount decimal.Decimal `json:"budgeted_amount"`
		ActualAmount   decimal.Decimal `json:"actual_amount"`
		Notes          string          `json:"notes"`
		ItemTier       models.ItemTier `json:"item_tier"`
	}
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	item, err := h.queries.UpdateBudgetItem(r.Context(), itemID, budgetID, req.BudgetedAmount, req.ActualAmount, req.Notes, req.ItemTier)
	if err != nil {
		writeError(w, http.StatusNotFound, "budget item not found")
		return
	}
	writeJSON(w, http.StatusOK, item)
}

func (h *Handlers) DeleteBudgetItem(w http.ResponseWriter, r *http.Request) {
	budgetID, err := parseUUID(chi.URLParam(r, "id"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid budget id")
		return
	}
	itemID, err := parseUUID(chi.URLParam(r, "itemId"))
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid item id")
		return
	}

	if err := h.queries.DeleteBudgetItem(r.Context(), itemID, budgetID); err != nil {
		writeError(w, http.StatusInternalServerError, "failed to delete budget item")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// Settings Handlers

func (h *Handlers) GetSettings(w http.ResponseWriter, r *http.Request) {
	userID := auth.UserIDFromContext(r.Context())
	user, err := h.queries.GetUserByID(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusNotFound, "user not found")
		return
	}
	writeJSON(w, http.StatusOK, user)
}

func (h *Handlers) UpdateSettings(w http.ResponseWriter, r *http.Request) {
	userID := auth.UserIDFromContext(r.Context())
	var req struct {
		DisplayName     string `json:"display_name"`
		PreferredLocale string `json:"preferred_locale"`
	}
	if err := decodeJSON(r, &req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	user, err := h.queries.UpdateUser(r.Context(), userID, req.DisplayName, req.PreferredLocale)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to update settings")
		return
	}
	writeJSON(w, http.StatusOK, user)
}