package handlers

import (
	"crypto/rand"
	"encoding/hex"
	"net/http"
	"regexp"
	"strconv"
	"strings"

	"github.com/flatrender/payment-svc/internal/db"
	"github.com/flatrender/payment-svc/internal/models"
	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
)

type AdminHandler struct {
	store *db.Store
}

func NewAdminHandler(store *db.Store) *AdminHandler { return &AdminHandler{store: store} }

var slugRe = regexp.MustCompile(`[^a-z0-9]+`)

func slugify(s string) string {
	s = strings.ToLower(strings.TrimSpace(s))
	s = slugRe.ReplaceAllString(s, "-")
	return strings.Trim(s, "-")
}

func randToken(prefix string) string {
	b := make([]byte, 24)
	_, _ = rand.Read(b)
	return prefix + hex.EncodeToString(b)
}

type clientInput struct {
	Name                 string   `json:"name"`
	Slug                 string   `json:"slug"`
	ZarinPalMerchantID   *string  `json:"zarinpal_merchant_id"`
	ZarinPalSandbox      *bool    `json:"zarinpal_sandbox"`
	AllowedReturnOrigins []string `json:"allowed_return_origins"`
	WebhookURL           *string  `json:"webhook_url"`
	IsActive             *bool    `json:"is_active"`
}

func (h *AdminHandler) List(c *gin.Context) {
	clients, err := h.store.ListClientApps(c.Request.Context())
	if err != nil {
		c.JSON(http.StatusInternalServerError, models.APIError{Code: "db_error", Message: err.Error()})
		return
	}
	if clients == nil {
		clients = []*models.ClientApp{}
	}
	c.JSON(http.StatusOK, gin.H{"data": clients})
}

func (h *AdminHandler) Create(c *gin.Context) {
	var in clientInput
	if err := c.ShouldBindJSON(&in); err != nil || strings.TrimSpace(in.Name) == "" {
		c.JSON(http.StatusBadRequest, models.APIError{Code: "bad_request", Message: "name is required"})
		return
	}
	slug := slugify(in.Slug)
	if slug == "" {
		slug = slugify(in.Name)
	}
	active := true
	if in.IsActive != nil {
		active = *in.IsActive
	}
	if in.AllowedReturnOrigins == nil {
		in.AllowedReturnOrigins = []string{}
	}
	client := &models.ClientApp{
		Name:                 in.Name,
		Slug:                 slug,
		APIKey:               randToken("pk_"),
		Secret:               randToken("sk_"),
		ZarinPalMerchantID:   in.ZarinPalMerchantID,
		ZarinPalSandbox:      in.ZarinPalSandbox,
		AllowedReturnOrigins: in.AllowedReturnOrigins,
		WebhookURL:           in.WebhookURL,
		IsActive:             active,
	}
	created, err := h.store.CreateClientApp(c.Request.Context(), client)
	if err != nil {
		if strings.Contains(err.Error(), "duplicate") || strings.Contains(err.Error(), "unique") {
			c.JSON(http.StatusConflict, models.APIError{Code: "conflict", Message: "slug already exists"})
			return
		}
		c.JSON(http.StatusInternalServerError, models.APIError{Code: "db_error", Message: err.Error()})
		return
	}
	// created includes the plaintext secret exactly once.
	c.JSON(http.StatusCreated, created)
}

func (h *AdminHandler) Get(c *gin.Context) {
	id, err := uuid.Parse(c.Param("id"))
	if err != nil {
		c.JSON(http.StatusBadRequest, models.APIError{Code: "bad_request", Message: "invalid id"})
		return
	}
	client, err := h.store.GetClientApp(c.Request.Context(), id)
	if err != nil {
		c.JSON(http.StatusNotFound, models.APIError{Code: "not_found", Message: "client not found"})
		return
	}
	c.JSON(http.StatusOK, client)
}

func (h *AdminHandler) Update(c *gin.Context) {
	id, err := uuid.Parse(c.Param("id"))
	if err != nil {
		c.JSON(http.StatusBadRequest, models.APIError{Code: "bad_request", Message: "invalid id"})
		return
	}
	existing, err := h.store.GetClientApp(c.Request.Context(), id)
	if err != nil {
		c.JSON(http.StatusNotFound, models.APIError{Code: "not_found", Message: "client not found"})
		return
	}
	var in clientInput
	if err := c.ShouldBindJSON(&in); err != nil {
		c.JSON(http.StatusBadRequest, models.APIError{Code: "bad_request", Message: "invalid body"})
		return
	}
	if in.Name != "" {
		existing.Name = in.Name
	}
	existing.ZarinPalMerchantID = in.ZarinPalMerchantID
	existing.ZarinPalSandbox = in.ZarinPalSandbox
	if in.AllowedReturnOrigins != nil {
		existing.AllowedReturnOrigins = in.AllowedReturnOrigins
	}
	existing.WebhookURL = in.WebhookURL
	if in.IsActive != nil {
		existing.IsActive = *in.IsActive
	}
	updated, err := h.store.UpdateClientApp(c.Request.Context(), id, existing)
	if err != nil {
		c.JSON(http.StatusInternalServerError, models.APIError{Code: "db_error", Message: err.Error()})
		return
	}
	c.JSON(http.StatusOK, updated)
}

func (h *AdminHandler) RotateSecret(c *gin.Context) {
	id, err := uuid.Parse(c.Param("id"))
	if err != nil {
		c.JSON(http.StatusBadRequest, models.APIError{Code: "bad_request", Message: "invalid id"})
		return
	}
	updated, err := h.store.RotateSecret(c.Request.Context(), id, randToken("sk_"))
	if err != nil {
		c.JSON(http.StatusNotFound, models.APIError{Code: "not_found", Message: "client not found"})
		return
	}
	c.JSON(http.StatusOK, updated) // includes the new secret once
}

func (h *AdminHandler) Delete(c *gin.Context) {
	id, err := uuid.Parse(c.Param("id"))
	if err != nil {
		c.JSON(http.StatusBadRequest, models.APIError{Code: "bad_request", Message: "invalid id"})
		return
	}
	if err := h.store.DeleteClientApp(c.Request.Context(), id); err != nil {
		c.JSON(http.StatusNotFound, models.APIError{Code: "not_found", Message: "client not found"})
		return
	}
	c.Status(http.StatusNoContent)
}

func (h *AdminHandler) ListTransactions(c *gin.Context) {
	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
	pageSize, _ := strconv.Atoi(c.DefaultQuery("page_size", "20"))
	if page < 1 {
		page = 1
	}
	if pageSize < 1 || pageSize > 200 {
		pageSize = 20
	}
	var clientID *uuid.UUID
	if cidStr := c.Query("client_id"); cidStr != "" {
		if cid, err := uuid.Parse(cidStr); err == nil {
			clientID = &cid
		}
	}
	txns, total, err := h.store.ListTransactions(c.Request.Context(), clientID, c.Query("status"), page, pageSize)
	if err != nil {
		c.JSON(http.StatusInternalServerError, models.APIError{Code: "db_error", Message: err.Error()})
		return
	}
	if txns == nil {
		txns = []*models.Transaction{}
	}
	c.JSON(http.StatusOK, gin.H{
		"data": txns,
		"meta": gin.H{"page": page, "page_size": pageSize, "total": total, "has_more": int64(page*pageSize) < total},
	})
}