package public

import (
	"crypto/rand"
	"encoding/hex"
	"net/http"
	"net/url"
	"strings"

	"github.com/gin-gonic/gin"
	"github.com/mattnite/forgejo-tickets/internal/auth"
	"github.com/rs/zerolog/log"
	"golang.org/x/oauth2"
)

type OAuthHandler struct {
	deps Dependencies
}

func (h *OAuthHandler) getProvider(providerName string) *auth.OAuthProvider {
	cfg := h.deps.Config
	baseURL := cfg.BaseURL

	switch providerName {
	case "google":
		if cfg.GoogleClientID == "" {
			return nil
		}
		return auth.NewGoogleProvider(cfg.GoogleClientID, cfg.GoogleClientSecret, baseURL+"/auth/google/callback")
	case "microsoft":
		if cfg.MicrosoftClientID == "" {
			return nil
		}
		return auth.NewMicrosoftProvider(cfg.MicrosoftClientID, cfg.MicrosoftClientSecret, cfg.MicrosoftTenantID, baseURL+"/auth/microsoft/callback")
	default:
		return nil
	}
}

func (h *OAuthHandler) Login(c *gin.Context) {
	providerName := c.Param("provider")

	// Handle Apple separately
	if providerName == "apple" {
		h.appleLogin(c)
		return
	}

	provider := h.getProvider(providerName)
	if provider == nil {
		c.String(http.StatusBadRequest, "Unknown provider")
		return
	}

	state := generateState()
	session, _ := h.deps.SessionStore.Get(c.Request, "oauth_state")
	session.Values["state"] = state
	session.Values["user_id"] = "00000000-0000-0000-0000-000000000000" // placeholder for save
	if err := session.Save(c.Request, c.Writer); err != nil {
		log.Error().Err(err).Msg("save oauth state error")
	}

	url := provider.Config.AuthCodeURL(state, oauth2.AccessTypeOffline)
	c.Redirect(http.StatusTemporaryRedirect, url)
}

func (h *OAuthHandler) Callback(c *gin.Context) {
	providerName := c.Param("provider")
	provider := h.getProvider(providerName)
	if provider == nil {
		c.String(http.StatusBadRequest, "Unknown provider")
		return
	}

	// Verify state
	session, _ := h.deps.SessionStore.Get(c.Request, "oauth_state")
	expectedState, _ := session.Values["state"].(string)
	if c.Query("state") != expectedState {
		c.String(http.StatusBadRequest, "Invalid state parameter")
		return
	}

	code := c.Query("code")
	token, err := provider.Config.Exchange(c.Request.Context(), code)
	if err != nil {
		log.Error().Err(err).Msg("oauth exchange error")
		c.String(http.StatusInternalServerError, "Authentication failed")
		return
	}

	info, err := provider.UserInfo(c.Request.Context(), token)
	if err != nil {
		log.Error().Err(err).Msg("oauth userinfo error")
		c.String(http.StatusInternalServerError, "Failed to get user info")
		return
	}

	user, err := h.deps.Auth.FindOrCreateOAuthUser(c.Request.Context(), provider.Name, info)
	if err != nil {
		if strings.Contains(err.Error(), "pending admin approval") {
			redirectURL := "/login?" + url.Values{
				"flash":      {err.Error()},
				"flash_type": {"info"},
			}.Encode()
			c.Redirect(http.StatusSeeOther, redirectURL)
			return
		}
		log.Error().Err(err).Msg("find or create oauth user error")
		c.String(http.StatusInternalServerError, "Authentication failed")
		return
	}

	if err := h.deps.Auth.CreateSession(c.Request, c.Writer, user.ID); err != nil {
		log.Error().Err(err).Msg("create session error")
		c.String(http.StatusInternalServerError, "Authentication failed")
		return
	}

	c.Redirect(http.StatusSeeOther, "/tickets")
}

func (h *OAuthHandler) appleLogin(c *gin.Context) {
	cfg := h.deps.Config
	if cfg.AppleClientID == "" {
		c.String(http.StatusBadRequest, "Apple Sign In not configured")
		return
	}

	appleProvider, err := auth.NewAppleProvider(
		cfg.AppleClientID, cfg.AppleTeamID, cfg.AppleKeyID, cfg.AppleKeyPath,
		cfg.BaseURL+"/auth/apple/callback",
	)
	if err != nil {
		log.Error().Err(err).Msg("create apple provider error")
		c.String(http.StatusInternalServerError, "Apple Sign In not available")
		return
	}

	state := generateState()
	session, _ := h.deps.SessionStore.Get(c.Request, "oauth_state")
	session.Values["state"] = state
	session.Values["user_id"] = "00000000-0000-0000-0000-000000000000"
	if err := session.Save(c.Request, c.Writer); err != nil {
		log.Error().Err(err).Msg("save oauth state error")
	}

	url := appleProvider.Config.AuthCodeURL(state, oauth2.AccessTypeOffline, auth.AppleAuthCodeOption())
	c.Redirect(http.StatusTemporaryRedirect, url)
}

func (h *OAuthHandler) AppleCallback(c *gin.Context) {
	cfg := h.deps.Config
	appleProvider, err := auth.NewAppleProvider(
		cfg.AppleClientID, cfg.AppleTeamID, cfg.AppleKeyID, cfg.AppleKeyPath,
		cfg.BaseURL+"/auth/apple/callback",
	)
	if err != nil {
		log.Error().Err(err).Msg("create apple provider error")
		c.String(http.StatusInternalServerError, "Apple Sign In not available")
		return
	}

	// Apple uses form_post
	code := c.PostForm("code")
	state := c.PostForm("state")

	session, _ := h.deps.SessionStore.Get(c.Request, "oauth_state")
	expectedState, _ := session.Values["state"].(string)
	if state != expectedState {
		c.String(http.StatusBadRequest, "Invalid state parameter")
		return
	}

	token, err := appleProvider.ExchangeCode(c.Request.Context(), code)
	if err != nil {
		log.Error().Err(err).Msg("apple exchange error")
		c.String(http.StatusInternalServerError, "Authentication failed")
		return
	}

	info, err := appleProvider.UserInfo(c.Request.Context(), token)
	if err != nil {
		log.Error().Err(err).Msg("apple userinfo error")
		c.String(http.StatusInternalServerError, "Failed to get user info")
		return
	}

	// Apple may send user data in the form
	if userData := c.PostForm("user"); userData != "" {
		appleUser, err := auth.ParseAppleUserData(userData)
		if err == nil && appleUser != nil && appleUser.Name != nil {
			info.Name = appleUser.Name.FirstName + " " + appleUser.Name.LastName
		}
	}

	user, err := h.deps.Auth.FindOrCreateOAuthUser(c.Request.Context(), "apple", info)
	if err != nil {
		if strings.Contains(err.Error(), "pending admin approval") {
			redirectURL := "/login?" + url.Values{
				"flash":      {err.Error()},
				"flash_type": {"info"},
			}.Encode()
			c.Redirect(http.StatusSeeOther, redirectURL)
			return
		}
		log.Error().Err(err).Msg("find or create apple user error")
		c.String(http.StatusInternalServerError, "Authentication failed")
		return
	}

	if err := h.deps.Auth.CreateSession(c.Request, c.Writer, user.ID); err != nil {
		log.Error().Err(err).Msg("create session error")
		c.String(http.StatusInternalServerError, "Authentication failed")
		return
	}

	c.Redirect(http.StatusSeeOther, "/tickets")
}

func generateState() string {
	b := make([]byte, 16)
	rand.Read(b)
	return hex.EncodeToString(b)
}