package handlers

import (
	"database/sql"
	"encoding/json"
	"log"
	"net/http"
	"strings"

	"github.com/gin-gonic/gin"
	"golang.org/x/crypto/bcrypt"

	"git.gobha.me/xcaliber/chat-switchboard/crypto"
	"git.gobha.me/xcaliber/chat-switchboard/database"
)

// ── Request Types ───────────────────────────

type updateProfileRequest struct {
	DisplayName *string `json:"display_name,omitempty"`
	Email       *string `json:"email,omitempty"`
}

type changePasswordRequest struct {
	CurrentPassword string `json:"current_password" binding:"required"`
	NewPassword     string `json:"new_password" binding:"required,min=8,max=128"`
}

type profileResponse struct {
	ID          string                 `json:"id"`
	Username    string                 `json:"username"`
	Email       string                 `json:"email"`
	DisplayName *string                `json:"display_name"`
	Role        string                 `json:"role"`
	Avatar      *string                `json:"avatar,omitempty"`
	Settings    map[string]interface{} `json:"settings"`
	CreatedAt   string                 `json:"created_at"`
}

// SettingsHandler manages user profile and preferences.
type SettingsHandler struct {
	uekCache *crypto.UEKCache
}

// NewSettingsHandler creates a new handler.
func NewSettingsHandler(uekCache *crypto.UEKCache) *SettingsHandler {
	return &SettingsHandler{uekCache: uekCache}
}

// ── Get Profile ─────────────────────────────

func (h *SettingsHandler) GetProfile(c *gin.Context) {
	userID := getUserID(c)

	var p profileResponse
	var settingsRaw string
	err := database.DB.QueryRow(database.Q(`
		SELECT id, username, email, display_name, role, avatar_url, settings::text, created_at
		FROM users WHERE id = $1
	`), userID).Scan(
		&p.ID, &p.Username, &p.Email, &p.DisplayName, &p.Role,
		&p.Avatar, &settingsRaw, &p.CreatedAt,
	)
	if err == sql.ErrNoRows {
		c.JSON(http.StatusNotFound, gin.H{"error": "user not found"})
		return
	}
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to load profile"})
		return
	}

	p.Settings = make(map[string]interface{})
	_ = json.Unmarshal([]byte(settingsRaw), &p.Settings)

	c.JSON(http.StatusOK, p)
}

// ── Update Profile ──────────────────────────

func (h *SettingsHandler) UpdateProfile(c *gin.Context) {
	userID := getUserID(c)

	var req updateProfileRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	if req.DisplayName != nil {
		_, err := database.DB.Exec(
			database.Q(`UPDATE users SET display_name = $1, updated_at = NOW() WHERE id = $2`),
			*req.DisplayName, userID,
		)
		if err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to update display name"})
			return
		}
	}

	if req.Email != nil {
		email := strings.ToLower(strings.TrimSpace(*req.Email))
		_, err := database.DB.Exec(
			database.Q(`UPDATE users SET email = $1, updated_at = NOW() WHERE id = $2`),
			email, userID,
		)
		if err != nil {
			if database.IsUniqueViolation(err) {
				c.JSON(http.StatusConflict, gin.H{"error": "email already taken"})
				return
			}
			c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to update email"})
			return
		}
	}

	h.GetProfile(c)
}

// ── Change Password ─────────────────────────

func (h *SettingsHandler) ChangePassword(c *gin.Context) {
	userID := getUserID(c)

	var req changePasswordRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	// Verify current password
	var hash string
	err := database.DB.QueryRow(
		database.Q(`SELECT password_hash FROM users WHERE id = $1`), userID,
	).Scan(&hash)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to verify password"})
		return
	}

	if err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(req.CurrentPassword)); err != nil {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "current password is incorrect"})
		return
	}

	// Hash new password
	newHash, err := bcrypt.GenerateFromPassword([]byte(req.NewPassword), bcryptCost)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to hash password"})
		return
	}

	_, err = database.DB.Exec(
		database.Q(`UPDATE users SET password_hash = $1, updated_at = NOW() WHERE id = $2`),
		string(newHash), userID,
	)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to update password"})
		return
	}

	// Re-wrap UEK with new password so personal BYOK keys remain accessible
	h.rewrapVault(userID, req.CurrentPassword, req.NewPassword)

	c.JSON(http.StatusOK, gin.H{"message": "password updated"})
}

// ── Get User Settings (JSONB) ───────────────

func (h *SettingsHandler) GetSettings(c *gin.Context) {
	userID := getUserID(c)

	var settingsRaw string
	err := database.DB.QueryRow(
		database.Q(`SELECT settings::text FROM users WHERE id = $1`), userID,
	).Scan(&settingsRaw)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to load settings"})
		return
	}

	settings := make(map[string]interface{})
	_ = json.Unmarshal([]byte(settingsRaw), &settings)

	c.JSON(http.StatusOK, settings)
}

// ── Update User Settings (JSONB merge) ──────

func (h *SettingsHandler) UpdateSettings(c *gin.Context) {
	userID := getUserID(c)

	var incoming map[string]interface{}
	if err := c.ShouldBindJSON(&incoming); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	patch, err := json.Marshal(incoming)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid settings"})
		return
	}

	// JSONB merge — existing keys preserved, incoming keys overwrite
	var mergeQuery string
	if database.IsSQLite() {
		mergeQuery = `UPDATE users SET settings = json_patch(settings, ?), updated_at = datetime('now') WHERE id = ?`
	} else {
		mergeQuery = `UPDATE users SET settings = settings || $1::jsonb, updated_at = NOW() WHERE id = $2`
	}
	_, err = database.DB.Exec(mergeQuery, string(patch), userID)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to update settings"})
		return
	}

	h.GetSettings(c)
}

// ── Vault Re-wrap ──────────────────────────

// rewrapVault decrypts the UEK with the old password and re-encrypts it with
// the new password. This keeps personal BYOK keys accessible after a password
// change. Uses a new salt for forward secrecy.
func (h *SettingsHandler) rewrapVault(userID, oldPassword, newPassword string) {
	if h.uekCache == nil {
		return
	}

	var vaultSet bool
	var encUEK, salt, nonce []byte
	err := database.DB.QueryRow(database.Q(`
		SELECT vault_set, encrypted_uek, uek_salt, uek_nonce
		FROM users WHERE id = $1
	`), userID).Scan(&vaultSet, &encUEK, &salt, &nonce)
	if err != nil || !vaultSet || len(encUEK) == 0 {
		return // No vault to re-wrap
	}

	// Decrypt UEK with old password
	oldPDK := crypto.DeriveKeyFromPassword(oldPassword, salt)
	uek, err := crypto.UnwrapUEK(encUEK, nonce, oldPDK)
	if err != nil {
		log.Printf("⚠ Vault re-wrap failed for user %s (unwrap): %v", userID, err)
		return
	}

	// Re-wrap with new password using fresh salt
	newSalt, err := crypto.GenerateSalt()
	if err != nil {
		log.Printf("⚠ Vault re-wrap failed for user %s (salt): %v", userID, err)
		return
	}

	newPDK := crypto.DeriveKeyFromPassword(newPassword, newSalt)
	newEncUEK, newNonce, err := crypto.WrapUEK(uek, newPDK)
	if err != nil {
		log.Printf("⚠ Vault re-wrap failed for user %s (wrap): %v", userID, err)
		return
	}

	_, err = database.DB.Exec(database.Q(`
		UPDATE users
		SET encrypted_uek = $1, uek_salt = $2, uek_nonce = $3, updated_at = NOW()
		WHERE id = $4
	`), newEncUEK, newSalt, newNonce, userID)
	if err != nil {
		log.Printf("⚠ Vault re-wrap failed for user %s (persist): %v", userID, err)
		return
	}

	// Session cache: UEK itself hasn't changed, just its wrapper
	h.uekCache.Store(userID, uek)
	log.Printf("  🔐 Vault re-wrapped for user %s", userID)
}