// Package handlers provides HTTP request handlers for ExpenseFlow.
//
// This file implements event management endpoints including dashboard
// listing, event creation, reopening, and expense viewing.
package handlers

import (
	"database/sql"
	"fmt"
	"html/template"
	"log"
	"net/http"
	"time"

	"github.com/expenseflow/internal/database"
	"github.com/expenseflow/internal/utils"
	"github.com/go-chi/chi/v5"
)

// ---------------------------------------------------------------------------
// EventHandler
// ---------------------------------------------------------------------------

// EventHandler groups HTTP handlers related to event management.
// It depends on a shared *sql.DB handle for database operations.
type EventHandler struct {
	DB *sql.DB
}

// NewEventHandler creates a new EventHandler with the given database handle.
func NewEventHandler(db *sql.DB) *EventHandler {
	return &EventHandler{DB: db}
}

// ---------------------------------------------------------------------------
// GET /dashboard — Dashboard
// ---------------------------------------------------------------------------

// Dashboard renders the main dashboard page showing all events belonging
// to the authenticated user, along with the new event creation form.
func (h *EventHandler) Dashboard(w http.ResponseWriter, r *http.Request) {
	userID := getUserID(r)
	if userID == "" {
		log.Printf("ERROR [%s] handlers: Dashboard: missing user ID", time.Now().Format(time.RFC3339))
		http.Error(w, "Unauthorized", http.StatusUnauthorized)
		return
	}

	events, err := database.GetEventsByUser(h.DB, userID)
	if err != nil {
		log.Printf("ERROR [%s] handlers: Dashboard: GetEventsByUser: %v",
			time.Now().Format(time.RFC3339), err)
		http.Error(w, "Failed to load events", http.StatusInternalServerError)
		return
	}

	tmpl, err := template.ParseFiles("templates/dashboard.html")
	if err != nil {
		log.Printf("ERROR [%s] handlers: Dashboard: parse template: %v",
			time.Now().Format(time.RFC3339), err)
		http.Error(w, "Internal server error", http.StatusInternalServerError)
		return
	}

	data := map[string]interface{}{
		"Events": events,
	}

	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := tmpl.Execute(w, data); err != nil {
		log.Printf("ERROR [%s] handlers: Dashboard: execute template: %v",
			time.Now().Format(time.RFC3339), err)
	}
}

// ---------------------------------------------------------------------------
// POST /events — CreateEvent
// ---------------------------------------------------------------------------

// CreateEvent handles the creation of a new event for the authenticated user.
// It reads the event name from the form, generates a UUID, persists the
// event, and redirects to the dashboard via HX-Redirect.
func (h *EventHandler) CreateEvent(w http.ResponseWriter, r *http.Request) {
	userID := getUserID(r)
	if userID == "" {
		log.Printf("ERROR [%s] handlers: CreateEvent: missing user ID", time.Now().Format(time.RFC3339))
		http.Error(w, "Unauthorized", http.StatusUnauthorized)
		return
	}

	name := r.FormValue("name")
	if name == "" {
		log.Printf("ERROR [%s] handlers: CreateEvent: missing event name", time.Now().Format(time.RFC3339))
		http.Error(w, "Event name is required", http.StatusBadRequest)
		return
	}

	id := utils.New()
	if err := database.CreateEvent(h.DB, id, userID, name); err != nil {
		log.Printf("ERROR [%s] handlers: CreateEvent: %v",
			time.Now().Format(time.RFC3339), err)
		http.Error(w, "Failed to create event", http.StatusInternalServerError)
		return
	}

	w.Header().Set("HX-Redirect", "/dashboard")
	w.WriteHeader(http.StatusOK)
}

// ---------------------------------------------------------------------------
// PUT /events/{id}/reopen — ReopenEvent
// ---------------------------------------------------------------------------

// ReopenEvent sets an event's status back to "open" and returns an HTMX
// fragment replacing the event's status badge with a green "open" badge.
// It verifies that the requesting user owns the event.
func (h *EventHandler) ReopenEvent(w http.ResponseWriter, r *http.Request) {
	eventID := chi.URLParam(r, "id")
	if eventID == "" {
		log.Printf("ERROR [%s] handlers: ReopenEvent: missing event ID",
			time.Now().Format(time.RFC3339))
		http.Error(w, "Missing event ID", http.StatusBadRequest)
		return
	}

	userID := getUserID(r)
	if userID == "" {
		log.Printf("ERROR [%s] handlers: ReopenEvent: missing user ID",
			time.Now().Format(time.RFC3339))
		http.Error(w, "Unauthorized", http.StatusUnauthorized)
		return
	}

	event, err := database.GetEventByID(h.DB, eventID)
	if err != nil {
		log.Printf("ERROR [%s] handlers: ReopenEvent: GetEventByID(%s): %v",
			time.Now().Format(time.RFC3339), eventID, err)
		http.Error(w, "Failed to retrieve event", http.StatusInternalServerError)
		return
	}
	if event == nil {
		log.Printf("ERROR [%s] handlers: ReopenEvent: event %s not found",
			time.Now().Format(time.RFC3339), eventID)
		http.Error(w, "Event not found", http.StatusNotFound)
		return
	}
	if event.UserID != userID {
		log.Printf("ERROR [%s] handlers: ReopenEvent: ownership mismatch for event %s",
			time.Now().Format(time.RFC3339), eventID)
		http.Error(w, "Forbidden", http.StatusForbidden)
		return
	}

	if err := database.UpdateEventStatus(h.DB, eventID, "open"); err != nil {
		log.Printf("ERROR [%s] handlers: ReopenEvent: UpdateEventStatus(%s): %v",
			time.Now().Format(time.RFC3339), eventID, err)
		http.Error(w, "Failed to reopen event", http.StatusInternalServerError)
		return
	}

	// Return HTMX fragment: green "open" badge targeting #status-badge-{id}.
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	fmt.Fprintf(w, `<span id="status-badge-%s" class="inline-flex items-center px-2.5 py-0.5 rounded-full text-xs font-medium bg-green-100 text-green-800">open</span>`, eventID)
}

// ---------------------------------------------------------------------------
// GET /events/{id}/expenses — ViewEventExpenses
// ---------------------------------------------------------------------------

// ViewEventExpenses displays the expense collection view for a specific event.
// It verifies event ownership, sets the current_event_id cookie, and renders
// the event_expenses.html template with the event and its expense list.
func (h *EventHandler) ViewEventExpenses(w http.ResponseWriter, r *http.Request) {
	eventID := chi.URLParam(r, "id")
	if eventID == "" {
		log.Printf("ERROR [%s] handlers: ViewEventExpenses: missing event ID",
			time.Now().Format(time.RFC3339))
		http.Error(w, "Missing event ID", http.StatusBadRequest)
		return
	}

	userID := getUserID(r)
	if userID == "" {
		log.Printf("ERROR [%s] handlers: ViewEventExpenses: missing user ID",
			time.Now().Format(time.RFC3339))
		http.Error(w, "Unauthorized", http.StatusUnauthorized)
		return
	}

	event, err := database.GetEventByID(h.DB, eventID)
	if err != nil {
		log.Printf("ERROR [%s] handlers: ViewEventExpenses: GetEventByID(%s): %v",
			time.Now().Format(time.RFC3339), eventID, err)
		http.Error(w, "Failed to retrieve event", http.StatusInternalServerError)
		return
	}
	if event == nil {
		log.Printf("ERROR [%s] handlers: ViewEventExpenses: event %s not found",
			time.Now().Format(time.RFC3339), eventID)
		http.Error(w, "Event not found", http.StatusNotFound)
		return
	}
	if event.UserID != userID {
		log.Printf("ERROR [%s] handlers: ViewEventExpenses: ownership mismatch for event %s",
			time.Now().Format(time.RFC3339), eventID)
		http.Error(w, "Forbidden", http.StatusForbidden)
		return
	}

	expenses, err := database.GetExpensesByEvent(h.DB, eventID)
	if err != nil {
		log.Printf("ERROR [%s] handlers: ViewEventExpenses: GetExpensesByEvent(%s): %v",
			time.Now().Format(time.RFC3339), eventID, err)
		http.Error(w, "Failed to load expenses", http.StatusInternalServerError)
		return
	}

	// Set the current_event_id cookie so subsequent expense operations
	// (SaveExpense, UploadReceipt) know which event to associate with.
	setCurrentEventID(w, eventID)

	tmpl, err := template.ParseFiles("templates/event_expenses.html")
	if err != nil {
		log.Printf("ERROR [%s] handlers: ViewEventExpenses: parse template: %v",
			time.Now().Format(time.RFC3339), err)
		http.Error(w, "Internal server error", http.StatusInternalServerError)
		return
	}

	data := map[string]interface{}{
		"Event":    event,
		"Expenses": expenses,
	}

	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := tmpl.Execute(w, data); err != nil {
		log.Printf("ERROR [%s] handlers: ViewEventExpenses: execute template: %v",
			time.Now().Format(time.RFC3339), err)
	}
}