package v1

import (
	"net/http"
	"net/url"

	"github.com/gin-gonic/gin"

	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/internal/service"
	"github.com/gochat/gochat/pkg/pagination"
	"github.com/gochat/gochat/pkg/response"
)

// PlatformUserHandler handles Platform API user endpoints (AccessToken auth).
// Reference: Chatwoot Platform::Api::V1::UsersController — AccessToken authenticated
//
// Distinct from SuperAdmin-platform routes: uses api_access_token header
// authentication + Permissible system for resource-level access control.
type PlatformUserHandler struct {
	svc *service.PlatformUserService
}

// NewPlatformUserHandler creates a new PlatformUser handler with service injection.
func NewPlatformUserHandler(svc *service.PlatformUserService) *PlatformUserHandler {
	return &PlatformUserHandler{svc: svc}
}

// Show retrieves a user by ID.
// GET /platform/api/v1/users/:id
// Reference: Chatwoot Platform::Api::V1::UsersController#show
// Requires: Permissible verification (PlatformApp must have access to this user)
func (h *PlatformUserHandler) Show(c *gin.Context) {
	userID, err := parseUintParam(c, "id")
	if err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid user ID")
		return
	}

	platformAppID := getPlatformAppID(c)

	user, err := h.svc.GetUserResponse(c.Request.Context(), platformAppID, userID)
	if err != nil {
		handlePlatformError(c, err)
		return
	}

	c.JSON(http.StatusOK, serializePlatformUser(user))
}

// Create creates a new user and auto-creates Permissible record.
// POST /platform/api/v1/users
// Reference: Chatwoot Platform::Api::V1::UsersController#create
// Auto-permissible: PlatformApp automatically gets access to the created user.
func (h *PlatformUserHandler) Create(c *gin.Context) {
	platformAppID := getPlatformAppID(c)

	var req service.PlatformUserRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, err.Error())
		return
	}
	if req.Email == "" {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "email is required")
		return
	}

	user, err := h.svc.CreateUser(c.Request.Context(), platformAppID, req)
	if err != nil {
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, err.Error())
		return
	}

	c.JSON(http.StatusOK, serializePlatformUser(user))
}

// Login generates an SSO login link for a user.
// GET /platform/api/v1/users/:id/login
// Reference: Chatwoot Platform::Api::V1::UsersController#login
// Returns: { url: sso_redirect_url }
func (h *PlatformUserHandler) Login(c *gin.Context) {
	userID, err := parseUintParam(c, "id")
	if err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid user ID")
		return
	}

	platformAppID := getPlatformAppID(c)

	user, err := h.svc.GetUserResponse(c.Request.Context(), platformAppID, userID)
	if err != nil {
		handlePlatformError(c, err)
		return
	}

	query := url.Values{}
	query.Set("email", user.User.Email)
	query.Set("sso_auth_token", user.AccessToken)
	c.JSON(http.StatusOK, gin.H{
		"url": "/app/login?" + query.Encode(),
	})
}

// Token returns the SSO authentication token for a user.
// POST /platform/api/v1/users/:id/token
// Reference: Chatwoot Platform::Api::V1::UsersController#token
// Returns: user resource with sso_auth_token field
func (h *PlatformUserHandler) Token(c *gin.Context) {
	userID, err := parseUintParam(c, "id")
	if err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid user ID")
		return
	}

	platformAppID := getPlatformAppID(c)

	// Verify Permissible access first
	if err := h.svc.ValidatePermissible(c.Request.Context(), platformAppID, userID); err != nil {
		handlePlatformError(c, err)
		return
	}

	user, err := h.svc.TokenResponse(c.Request.Context(), platformAppID, userID)
	if err != nil {
		handlePlatformError(c, err)
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"access_token": user.AccessToken,
		"expiry":       nil,
		"user": gin.H{
			"id":           user.User.ID,
			"name":         user.User.Name,
			"display_name": user.User.DisplayName,
			"email":        user.User.Email,
			"pubsub_token": user.User.PubsubToken,
		},
	})
}

// Update updates a user.
// PATCH /platform/api/v1/users/:id
// Reference: Chatwoot Platform::Api::V1::UsersController#update
// Requires: Permissible verification
func (h *PlatformUserHandler) Update(c *gin.Context) {
	userID, err := parseUintParam(c, "id")
	if err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid user ID")
		return
	}

	platformAppID := getPlatformAppID(c)

	var req service.PlatformUserRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, err.Error())
		return
	}

	user, err := h.svc.UpdateUser(c.Request.Context(), platformAppID, userID, req)
	if err != nil {
		handlePlatformError(c, err)
		return
	}

	c.JSON(http.StatusOK, serializePlatformUser(user))
}

// Destroy deletes a user.
// DELETE /platform/api/v1/users/:id
// Reference: Chatwoot Platform::Api::V1::UsersController#destroy
// Requires: Permissible verification
func (h *PlatformUserHandler) Destroy(c *gin.Context) {
	userID, err := parseUintParam(c, "id")
	if err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid user ID")
		return
	}

	platformAppID := getPlatformAppID(c)

	if err := h.svc.DeleteUser(c.Request.Context(), platformAppID, userID); err != nil {
		handlePlatformError(c, err)
		return
	}

	c.Status(http.StatusOK)
}

func serializePlatformUser(payload *service.PlatformUserResponse) gin.H {
	if payload == nil {
		return gin.H{}
	}
	user := payload.User
	out := gin.H{
		"access_token":      payload.AccessToken,
		"account_id":        activeAccountID(payload.AccountUsers),
		"available_name":    nonEmpty(user.DisplayName, user.Name),
		"avatar_url":        user.AvatarURL,
		"confirmed":         user.ConfirmedAt != nil,
		"display_name":      user.DisplayName,
		"message_signature": user.MessageSignature,
		"email":             user.Email,
		"id":                user.ID,
		"name":              user.Name,
		"provider":          nonEmpty(user.Provider, "email"),
		"pubsub_token":      user.PubsubToken,
		"role":              activeAccountRole(payload.AccountUsers),
		"ui_settings":       jsonObject(user.UISettings),
		"uid":               user.UID,
		"accounts":          serializePlatformUserAccounts(payload.AccountUsers),
	}
	if attrs := jsonObject(user.CustomAttributes); len(attrs) > 0 {
		out["custom_attributes"] = attrs
	}
	return out
}

func serializePlatformUserAccounts(accountUsers []model.AccountUser) []gin.H {
	accounts := make([]gin.H, 0, len(accountUsers))
	for _, au := range accountUsers {
		accounts = append(accounts, gin.H{
			"id":        au.AccountID,
			"name":      au.Account.Name,
			"active_at": au.ActiveAt,
			"role":      au.Role,
		})
	}
	return accounts
}

func activeAccountID(accountUsers []model.AccountUser) any {
	if len(accountUsers) == 0 {
		return nil
	}
	return accountUsers[0].AccountID
}

func activeAccountRole(accountUsers []model.AccountUser) any {
	if len(accountUsers) == 0 {
		return nil
	}
	return accountUsers[0].Role
}

// --- Helper functions for Platform API handlers ---

// getPlatformAppID extracts platform_app_id from the Gin context.
// Set by PlatformAppAuth middleware during AccessToken authentication.
func getPlatformAppID(c *gin.Context) uint {
	if id, exists := c.Get("platform_app_id"); exists {
		switch v := id.(type) {
		case uint:
			return v
		case float64:
			return uint(v)
		case int:
			return uint(v)
		}
	}
	return 0
}

// handlePlatformError maps service errors to HTTP responses.
func handlePlatformError(c *gin.Context, err error) {
	if err.Error() == "non permissible resource" {
		response.AbortWithStatusError(c, http.StatusForbidden, response.ErrForbidden, "non permissible resource")
		return
	}
	response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, err.Error())
}

// PlatformUsersListHandler returns all users the PlatformApp has permissible access to.
// GET /platform/api/v1/users
// Reference: Chatwoot Platform::Api::V1::UsersController#index (lists permissibles)
func (h *PlatformUserHandler) List(c *gin.Context) {
	platformAppID := getPlatformAppID(c)
	page := pagination.Parse(c)

	users, err := h.svc.ListPermissibleUsers(c.Request.Context(), platformAppID)
	if err != nil {
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, err.Error())
		return
	}

	// Manual pagination since we filter by permissible first
	total := int64(len(users))
	start := page.Offset
	if start > len(users) {
		start = len(users)
	}
	end := start + page.PerPage
	if end > len(users) {
		end = len(users)
	}

	response.OKWithMeta(c, users[start:end], page.Page, page.PerPage, total)
}