package pay

import (
	"database/sql"
	"encoding/json"
	"errors"
	"io"
	"log/slog"
	"net/http"
	"time"

	"github.com/go-chi/chi/v5"

	"github.com/wangjia/pangolin/server/internal/apierr"
	"github.com/wangjia/pangolin/server/internal/auth"
)

// Handler 是面向 App 的下单代理(JWT 保护;user→biz_ref 映射在 server 侧,
// 客户端只传 sku+method+端型 metadata,永远不传金额)。
type Handler struct {
	client *Client
	store  *Store
	db     *sql.DB
}

func NewHandler(client *Client, store *Store, db *sql.DB) *Handler {
	return &Handler{client: client, store: store, db: db}
}

// allowedMetadataKeys 与 pay gateway.go 白名单一致(is_mobile/render)。
var allowedMetadataKeys = map[string]bool{"is_mobile": true, "render": true}

func filterMetadata(in map[string]string) map[string]string {
	if len(in) == 0 {
		return nil
	}
	out := make(map[string]string, len(in))
	for k, v := range in {
		if allowedMetadataKeys[k] {
			out[k] = v
		}
	}
	if len(out) == 0 {
		return nil
	}
	return out
}

func writeJSON(w http.ResponseWriter, v any) {
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(v)
}

// writePayErr 把 pay 网关错误映射为 apierr(脱敏双语;code 透传供客户端分辨)。
func writePayErr(w http.ResponseWriter, err error) {
	var pe *Error
	if !errors.As(err, &pe) {
		apierr.WriteJSON(w, http.StatusBadGateway,
			apierr.New("PAY_UPSTREAM", "支付服务暂不可用，请稍后重试", "Payment service unavailable, please retry later"))
		return
	}
	switch pe.Code {
	case "currency_mismatch":
		apierr.WriteJSON(w, http.StatusConflict,
			apierr.New("CURRENCY_MISMATCH", "该支付方式结算币种与订单不符，请重新下单", "Settlement currency mismatch, please create a new order"))
	case "order_not_pending":
		apierr.WriteJSON(w, http.StatusConflict,
			apierr.New("ORDER_NOT_PENDING", "订单状态已变化，请刷新后重试", "Order is no longer pending"))
	case "order_not_found", "product_not_found":
		apierr.WriteJSON(w, http.StatusNotFound, apierr.ErrNotFound)
	case "rate_limited":
		apierr.WriteJSON(w, http.StatusTooManyRequests, apierr.ErrRateLimited)
	case "unknown_method", "bad_request", "method_not_recurring":
		apierr.WriteJSON(w, http.StatusBadRequest, apierr.ErrBadRequest)
	default: // no_account / no_settle_currency / create_failed / upstream_error…
		apierr.WriteJSON(w, http.StatusBadGateway,
			apierr.New("PAY_UPSTREAM", "支付服务暂不可用，请稍后重试", "Payment service unavailable, please retry later"))
	}
}

// ─── GET /v1/pay/catalog ────────────────────────────────────────────────────

func (h *Handler) Catalog(w http.ResponseWriter, _ *http.Request) {
	writeJSON(w, map[string]any{"items": Catalog})
}

// ─── POST /v1/pay/orders ────────────────────────────────────────────────────

type createOrderRequest struct {
	SKU      string            `json:"sku"`
	Method   string            `json:"method"`
	Metadata map[string]string `json:"metadata,omitempty"`
}

type sessionResponse struct {
	OrderNo string  `json:"order_no"`
	Session Session `json:"session"`
}

func (h *Handler) CreateOrder(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	uid, ok := auth.UserIDFromContext(ctx)
	if !ok {
		apierr.WriteJSON(w, http.StatusUnauthorized, apierr.ErrUnauthorized)
		return
	}
	var req createOrderRequest
	if err := json.NewDecoder(io.LimitReader(r.Body, 16<<10)).Decode(&req); err != nil {
		apierr.WriteJSON(w, http.StatusBadRequest, apierr.ErrBadRequest)
		return
	}
	if _, ok := CatalogBySKU(req.SKU); !ok || req.Method == "" {
		apierr.WriteJSON(w, http.StatusBadRequest, apierr.ErrBadRequest)
		return
	}
	var bizRef string
	err := h.db.QueryRowContext(ctx,
		`SELECT uuid FROM users WHERE id = ? AND status = 'active'`, uid).Scan(&bizRef)
	if err == sql.ErrNoRows {
		apierr.WriteJSON(w, http.StatusNotFound, apierr.ErrNotFound)
		return
	} else if err != nil {
		apierr.WriteJSON(w, http.StatusInternalServerError, apierr.ErrInternal)
		return
	}

	res, err := h.client.CreateOrder(ctx, req.SKU, req.Method, bizRef, filterMetadata(req.Metadata))
	if err != nil {
		writePayErr(w, err)
		return
	}
	if err := h.store.Insert(ctx, uid, bizRef, req.SKU, res.OrderNo, req.Method); err != nil {
		// 不吞单:webhook 会按 biz_ref 兜底补台账,这里记日志便于追查。
		slog.Error("pay: 台账写入失败(webhook 将按 biz_ref 兜底)", "order_no", res.OrderNo, "err", err)
	}
	writeJSON(w, sessionResponse{OrderNo: res.OrderNo, Session: res.Session})
}

// ─── GET /v1/pay/orders/{orderNo} ───────────────────────────────────────────

type orderStatusResponse struct {
	OrderNo   string  `json:"order_no"`
	PayStatus string  `json:"pay_status"` // pay 侧状态词汇原样透传
	Activated bool    `json:"activated"`  // 本地台账已消费(权益已开通)——客户端轮询以此为成功判据
	ExpiresAt *string `json:"expires_at,omitempty"`
}

func (h *Handler) GetOrder(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	uid, ok := auth.UserIDFromContext(ctx)
	if !ok {
		apierr.WriteJSON(w, http.StatusUnauthorized, apierr.ErrUnauthorized)
		return
	}
	orderNo := chi.URLParam(r, "orderNo")
	row, err := h.store.GetForUser(ctx, uid, orderNo)
	if err == sql.ErrNoRows {
		apierr.WriteJSON(w, http.StatusNotFound, apierr.ErrNotFound)
		return
	} else if err != nil {
		apierr.WriteJSON(w, http.StatusInternalServerError, apierr.ErrInternal)
		return
	}
	st, err := h.client.GetOrder(ctx, orderNo)
	if err != nil {
		writePayErr(w, err)
		return
	}
	resp := orderStatusResponse{OrderNo: orderNo, PayStatus: st.Status, Activated: row.Status == "paid"}
	if row.SubID.Valid {
		if exp, err := h.store.SubscriptionExpiry(ctx, row.SubID.Int64); err == nil {
			s := exp.UTC().Format(time.RFC3339)
			resp.ExpiresAt = &s
		}
	}
	writeJSON(w, resp)
}

// ─── POST /v1/pay/orders/{orderNo}/retry ────────────────────────────────────

type retryOrderRequest struct {
	Method   string            `json:"method"`
	Metadata map[string]string `json:"metadata,omitempty"`
}

func (h *Handler) Retry(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	uid, ok := auth.UserIDFromContext(ctx)
	if !ok {
		apierr.WriteJSON(w, http.StatusUnauthorized, apierr.ErrUnauthorized)
		return
	}
	orderNo := chi.URLParam(r, "orderNo")
	var req retryOrderRequest
	if err := json.NewDecoder(io.LimitReader(r.Body, 16<<10)).Decode(&req); err != nil || req.Method == "" {
		apierr.WriteJSON(w, http.StatusBadRequest, apierr.ErrBadRequest)
		return
	}
	if _, err := h.store.GetForUser(ctx, uid, orderNo); err == sql.ErrNoRows {
		apierr.WriteJSON(w, http.StatusNotFound, apierr.ErrNotFound)
		return
	} else if err != nil {
		apierr.WriteJSON(w, http.StatusInternalServerError, apierr.ErrInternal)
		return
	}
	res, err := h.client.Retry(ctx, orderNo, req.Method, filterMetadata(req.Metadata))
	if err != nil {
		writePayErr(w, err)
		return
	}
	_ = h.store.UpdateMethod(ctx, uid, orderNo, req.Method)
	writeJSON(w, sessionResponse{OrderNo: res.OrderNo, Session: res.Session})
}

// ─── POST /v1/pay/orders/{orderNo}/cancel ───────────────────────────────────

func (h *Handler) Cancel(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	uid, ok := auth.UserIDFromContext(ctx)
	if !ok {
		apierr.WriteJSON(w, http.StatusUnauthorized, apierr.ErrUnauthorized)
		return
	}
	orderNo := chi.URLParam(r, "orderNo")
	if _, err := h.store.GetForUser(ctx, uid, orderNo); err == sql.ErrNoRows {
		apierr.WriteJSON(w, http.StatusNotFound, apierr.ErrNotFound)
		return
	} else if err != nil {
		apierr.WriteJSON(w, http.StatusInternalServerError, apierr.ErrInternal)
		return
	}
	canceled, err := h.client.Cancel(ctx, orderNo)
	if err != nil {
		writePayErr(w, err)
		return
	}
	if canceled {
		_ = h.store.MarkCanceled(ctx, uid, orderNo)
	}
	writeJSON(w, map[string]bool{"canceled": canceled})
}