package upstream

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"cmpp-platform/gateway/internal/queue"
)

type drainageBusinessRejection struct{ reason string }

func (e *drainageBusinessRejection) Error() string { return "引流资格拒绝: " + e.reason }

// Recheck current DB authorization after queue/connection waits. Neither a stale
// command nor a disabled detection flag on a command can grant permission.
func (m *Manager) authorizeDrainage(ctx context.Context, cmd queue.SubmitCommand) error {
	if !m.DrainageGuardEnabled {
		return nil
	}
	digest := sha256.Sum256([]byte(cmd.Content))
	body, err := json.Marshal(map[string]string{"submitId": cmd.SubmitID, "channelId": cmd.ChannelID, "contentHash": hex.EncodeToString(digest[:])})
	if err != nil {
		return err
	}
	base := m.EventAPIBaseURL
	if base == "" {
		base = m.APIBaseURL
	}
	if base == "" {
		return fmt.Errorf("引流资格校验服务未配置")
	}
	checkCtx, cancel := context.WithTimeout(ctx, 10*time.Second)
	defer cancel()
	req, err := http.NewRequestWithContext(checkCtx, http.MethodPost, strings.TrimRight(base, "/")+"/gateway/events/authorize-drainage", bytes.NewReader(body))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")
	client := m.HTTPClient
	if client == nil {
		client = &http.Client{Timeout: 10 * time.Second}
	}
	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("引流资格校验暂不可用: %w", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated {
		return fmt.Errorf("引流资格校验失败: HTTP %d", resp.StatusCode)
	}
	var result struct {
		Allowed bool   `json:"allowed"`
		Reason  string `json:"reason"`
	}
	if err := json.NewDecoder(io.LimitReader(resp.Body, 16384)).Decode(&result); err != nil {
		return fmt.Errorf("引流资格响应无效: %w", err)
	}
	if !result.Allowed {
		return &drainageBusinessRejection{reason: result.Reason}
	}
	return nil
}