package handlers

import (
	"crypto/subtle"
	"net/http"
	"net/url"
	"strconv"
	"time"

	"sneak.berlin/go/pixa/internal/encurl"
	"sneak.berlin/go/pixa/internal/imgcache"
	"sneak.berlin/go/pixa/internal/templates"
)

// HandleRoot serves the login page or generator page based on authentication state.
func (s *Handlers) HandleRoot() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		// Check if signing key is configured
		if s.sessMgr == nil {
			s.respondError(w, "signing key not configured", http.StatusServiceUnavailable)

			return
		}

		if r.Method == http.MethodPost {
			s.handleLoginPost(w, r)

			return
		}

		// Check if authenticated
		if s.sessMgr.IsAuthenticated(r) {
			s.renderGenerator(w, nil)

			return
		}

		// Show login page
		s.renderLogin(w, "")
	}
}

// handleLoginPost handles login form submission.
func (s *Handlers) handleLoginPost(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		s.renderLogin(w, "Invalid form data")

		return
	}

	submittedKey := r.FormValue("key")

	// Constant-time comparison to prevent timing attacks
	if subtle.ConstantTimeCompare([]byte(submittedKey), []byte(s.config.SigningKey)) != 1 {
		s.log.Warn("failed login attempt", "remote_addr", r.RemoteAddr)
		s.renderLogin(w, "Invalid signing key")

		return
	}

	// Create session
	if err := s.sessMgr.CreateSession(w); err != nil {
		s.log.Error("failed to create session", "error", err)
		s.renderLogin(w, "Failed to create session")

		return
	}

	s.log.Info("successful login", "remote_addr", r.RemoteAddr)

	// Redirect to generator page
	http.Redirect(w, r, "/", http.StatusSeeOther)
}

// HandleLogout clears the session and redirects to login.
func (s *Handlers) HandleLogout() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if s.sessMgr != nil {
			s.sessMgr.ClearSession(w)
		}

		http.Redirect(w, r, "/", http.StatusSeeOther)
	}
}

// HandleGenerateURL handles the URL generation form submission.
func (s *Handlers) HandleGenerateURL() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		// Check authentication
		if s.sessMgr == nil || !s.sessMgr.IsAuthenticated(r) {
			http.Redirect(w, r, "/", http.StatusSeeOther)

			return
		}

		if err := r.ParseForm(); err != nil {
			s.renderGenerator(w, &generatorData{Error: "Invalid form data"})

			return
		}

		// Parse form values
		sourceURL := r.FormValue("url")
		widthStr := r.FormValue("width")
		heightStr := r.FormValue("height")
		format := r.FormValue("format")
		qualityStr := r.FormValue("quality")
		fit := r.FormValue("fit")
		ttlStr := r.FormValue("ttl")

		// Validate source URL
		parsed, err := url.Parse(sourceURL)
		if err != nil || parsed.Host == "" {
			s.renderGeneratorWithForm(w, "Invalid source URL", r.Form)

			return
		}

		// Parse dimensions
		width, _ := strconv.Atoi(widthStr)
		height, _ := strconv.Atoi(heightStr)
		quality, _ := strconv.Atoi(qualityStr)
		ttl, _ := strconv.Atoi(ttlStr)

		if quality <= 0 {
			quality = 85
		}

		if ttl <= 0 {
			ttl = 2592000 // 30 days default
		}

		// Create payload
		expiresAt := time.Now().Add(time.Duration(ttl) * time.Second)
		payload := &encurl.Payload{
			SourceHost:  parsed.Host,
			SourcePath:  parsed.Path,
			SourceQuery: parsed.RawQuery,
			Width:       width,
			Height:      height,
			Format:      imgcache.ImageFormat(format),
			Quality:     quality,
			FitMode:     imgcache.FitMode(fit),
			ExpiresAt:   expiresAt.Unix(),
		}

		// Generate encrypted token
		token, err := s.encGen.Generate(payload)
		if err != nil {
			s.log.Error("failed to generate encrypted URL", "error", err)
			s.renderGeneratorWithForm(w, "Failed to generate URL", r.Form)

			return
		}

		// Build full URL
		scheme := "https"
		if s.config.Debug {
			scheme = "http"
		}

		host := r.Host
		generatedURL := scheme + "://" + host + "/v1/e/" + token

		s.renderGenerator(w, &generatorData{
			GeneratedURL: generatedURL,
			ExpiresAt:    expiresAt.Format(time.RFC3339),
			FormURL:      sourceURL,
			FormWidth:    widthStr,
			FormHeight:   heightStr,
			FormFormat:   format,
			FormQuality:  qualityStr,
			FormFit:      fit,
			FormTTL:      ttlStr,
		})
	}
}

// generatorData holds template data for the generator page.
type generatorData struct {
	GeneratedURL string
	ExpiresAt    string
	Error        string
	FormURL      string
	FormWidth    string
	FormHeight   string
	FormFormat   string
	FormQuality  string
	FormFit      string
	FormTTL      string
}

func (s *Handlers) renderLogin(w http.ResponseWriter, errorMsg string) {
	w.Header().Set("Content-Type", "text/html; charset=utf-8")

	data := struct {
		Error string
	}{
		Error: errorMsg,
	}

	if err := templates.Render(w, "login.html", data); err != nil {
		s.log.Error("failed to render login template", "error", err)
		http.Error(w, "Internal server error", http.StatusInternalServerError)
	}
}

func (s *Handlers) renderGenerator(w http.ResponseWriter, data *generatorData) {
	w.Header().Set("Content-Type", "text/html; charset=utf-8")

	if data == nil {
		data = &generatorData{}
	}

	if err := templates.Render(w, "generator.html", data); err != nil {
		s.log.Error("failed to render generator template", "error", err)
		http.Error(w, "Internal server error", http.StatusInternalServerError)
	}
}

func (s *Handlers) renderGeneratorWithForm(w http.ResponseWriter, errorMsg string, form url.Values) {
	s.renderGenerator(w, &generatorData{
		Error:       errorMsg,
		FormURL:     form.Get("url"),
		FormWidth:   form.Get("width"),
		FormHeight:  form.Get("height"),
		FormFormat:  form.Get("format"),
		FormQuality: form.Get("quality"),
		FormFit:     form.Get("fit"),
		FormTTL:     form.Get("ttl"),
	})
}