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
	}
	item, ok := CatalogBySKU(req.SKU)
	if !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
	}

	// 优惠档(Promo SKU)每账号限购一次:该用户已有该 SKU 的 paid 台账则拒单,
	// 不打上游(真机实测发现用户可反复购买优惠档)。Retry/Cancel 不受限——恢复原单不受限。
	if item.Promo {
		used, err := h.store.HasPaidPurchase(ctx, uid, req.SKU)
		if err != nil {
			apierr.WriteJSON(w, http.StatusInternalServerError, apierr.ErrInternal)
			return
		}
		if used {
			apierr.WriteJSON(w, http.StatusConflict,
				apierr.New("PROMO_ALREADY_USED", "优惠套餐每个账号限购一次，你已购买过", "This promotional plan is limited to one per account and you have already purchased it"))
			return
		}
	}

	res, err := h.client.CreateOrder(ctx, req.SKU, req.Method, bizRef, filterMetadata(req.Metadata))
	if err != nil {
		writePayErr(w, err)
		return
	}
	// 下单即落展示金额/结算币种(按支付方式);webhook 到账后由实际结算金额覆盖。
	amount := DisplayAmountMinor(item, req.Method)
	currency := SettlementCurrency(req.Method)
	if err := h.store.Insert(ctx, uid, bizRef, req.SKU, res.OrderNo, req.Method, amount, currency); 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 (列表) ──────────────────────────────────────────────

// orderView 是订单的台账视图(列表/详情共用富字段;金额为结算币种 minor:CNY 分 / USDT 微元)。
type orderView struct {
	OrderNo     string  `json:"order_no"`
	SKU         string  `json:"sku"`
	Plan        string  `json:"plan"`
	Days        int     `json:"days"`
	Method      string  `json:"method"`
	Status      string  `json:"status"` // 本地台账:created | paid | canceled
	AmountMinor int64   `json:"amount_minor"`
	Currency    string  `json:"currency"`
	Channel     string  `json:"channel,omitempty"`
	CreatedAt   string  `json:"created_at"` // RFC3339
	PaidAt      *string `json:"paid_at,omitempty"`
}

// 未付订单展示层过期窗口(近似 pay 会话时效;仅影响列表/详情显示,不改台账)。
const orderPendingTTL = 30 * time.Minute

func orderViewFromRow(row *PurchaseRow) orderView {
	v := orderView{
		OrderNo: row.OutTradeNo, SKU: row.SKU, Method: row.Method, Status: row.Status,
		AmountMinor: row.AmountMinor, Currency: row.Currency, Channel: row.Channel,
		CreatedAt: row.CreatedAt.UTC().Format(time.RFC3339),
	}
	if it, ok := CatalogBySKU(row.SKU); ok {
		v.Plan, v.Days = it.Plan, it.Days
		// 展示金额兜底:老单/webhook 前 amount_minor=0(旧下单不落金额)→ 按档位+
		// 支付方式的结算币种回退到展示价,列表/详情不再显 0。webhook 到账后为实际金额,不触发。
		if v.AmountMinor == 0 {
			v.AmountMinor = DisplayAmountMinor(it, row.Method)
			if v.Currency == "" {
				v.Currency = SettlementCurrency(row.Method)
			}
		}
	}
	if row.PaidAt.Valid {
		s := row.PaidAt.Time.UTC().Format(time.RFC3339)
		v.PaidAt = &s
	}
	if row.Status == "created" && row.CreatedAt.Add(orderPendingTTL).Before(time.Now()) {
		v.Status = "expired" // 展示层:台账仍 created,可继续支付/取消
	}
	return v
}

// List 列出当前用户历史订单(倒序;纯本地台账,不逐单回查 pay 上游)。
func (h *Handler) List(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	uid, ok := auth.UserIDFromContext(ctx)
	if !ok {
		apierr.WriteJSON(w, http.StatusUnauthorized, apierr.ErrUnauthorized)
		return
	}
	rows, err := h.store.ListByUser(ctx, uid, 100)
	if err != nil {
		apierr.WriteJSON(w, http.StatusInternalServerError, apierr.ErrInternal)
		return
	}
	out := make([]orderView, 0, len(rows))
	for i := range rows {
		out = append(out, orderViewFromRow(&rows[i]))
	}
	writeJSON(w, map[string]any{"orders": out})
}

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

type orderStatusResponse struct {
	orderView
	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{orderView: orderViewFromRow(row), 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})
}