package auth

import (
	"context"
	"log"
	"net/http"
	"os"

	"github.com/coreos/go-oidc/v3/oidc"
	"github.com/gin-gonic/gin"
	"golang.org/x/oauth2"
)

var (
	oidcProvider *oidc.Provider
	oauth2Cfg    *oauth2.Config
	authEnabled  bool
)

func InitOIDC(ctx context.Context) error {
	issuer := os.Getenv("OIDC_ISSUER")
	if issuer == "" {
		log.Println("OIDC_ISSUER not set; authentication disabled")
		return nil
	}

	p, err := oidc.NewProvider(ctx, issuer)
	if err != nil {
		return err
	}
	oidcProvider = p
	oauth2Cfg = &oauth2.Config{
		ClientID:     os.Getenv("OIDC_CLIENT_ID"),
		ClientSecret: os.Getenv("OIDC_CLIENT_SECRET"),
		RedirectURL:  os.Getenv("OIDC_REDIRECT_URL"),
		Endpoint:     p.Endpoint(),
		Scopes:       []string{oidc.ScopeOpenID, "profile", "email"},
	}
	authEnabled = true
	log.Println("OIDC authentication enabled")
	return nil
}

func Enabled() bool { return authEnabled }

func HandleLogin(c *gin.Context) {
	state, err := randomHex(16)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "state generation failed"})
		return
	}
	if err := SaveState(c.Request.Context(), state); err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "state save failed"})
		return
	}
	c.Redirect(http.StatusFound, oauth2Cfg.AuthCodeURL(state))
}

func HandleCallback(c *gin.Context) {
	ctx := c.Request.Context()

	if !ConsumeState(ctx, c.Query("state")) {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid state"})
		return
	}

	token, err := oauth2Cfg.Exchange(ctx, c.Query("code"))
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "token exchange failed"})
		return
	}

	rawIDToken, ok := token.Extra("id_token").(string)
	if !ok {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "missing id_token"})
		return
	}

	verifier := oidcProvider.Verifier(&oidc.Config{ClientID: oauth2Cfg.ClientID})
	idToken, err := verifier.Verify(ctx, rawIDToken)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "token verification failed"})
		return
	}

	var claims struct {
		Sub   string `json:"sub"`
		Email string `json:"email"`
		Name  string `json:"name"`
	}
	if err := idToken.Claims(&claims); err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "claims extraction failed"})
		return
	}

	sessionID, err := SaveSession(ctx, &Session{
		UserID: claims.Sub,
		Email:  claims.Email,
		Name:   claims.Name,
	})
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "session save failed"})
		return
	}

	secure := c.Request.TLS != nil || c.GetHeader("X-Forwarded-Proto") == "https"
	http.SetCookie(c.Writer, &http.Cookie{
		Name:     sessionCookieName,
		Value:    sessionID,
		Path:     "/",
		HttpOnly: true,
		Secure:   secure,
		SameSite: http.SameSiteLaxMode,
		MaxAge:   int(sessionTTL.Seconds()),
	})

	frontendURL := os.Getenv("PUBLIC_HOST")
	if frontendURL == "" {
		frontendURL = "/"
	}
	c.Redirect(http.StatusFound, frontendURL)
}

func HandleLogout(c *gin.Context) {
	if cookie, err := c.Request.Cookie(sessionCookieName); err == nil {
		_ = DeleteSession(c.Request.Context(), cookie.Value)
	}
	http.SetCookie(c.Writer, &http.Cookie{
		Name:     sessionCookieName,
		Value:    "",
		Path:     "/",
		HttpOnly: true,
		MaxAge:   -1,
	})
	c.Redirect(http.StatusFound, "/")
}

func HandleMe(c *gin.Context) {
	if !authEnabled {
		c.JSON(http.StatusOK, gin.H{"auth_enabled": false})
		return
	}
	cookie, err := c.Request.Cookie(sessionCookieName)
	if err != nil {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "not authenticated"})
		return
	}
	sess, err := GetSession(c.Request.Context(), cookie.Value)
	if err != nil {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "session expired"})
		return
	}
	c.JSON(http.StatusOK, sess)
}