package httpapi

import (
	"bufio"
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"rk3588sys/agent/internal/files"
)

type alarmRecord struct {
	ID          string  `json:"id"`
	Timestamp   string  `json:"timestamp"`
	Channel     string  `json:"channel"`
	RuleName    string  `json:"rule_name"`
	RuleType    string  `json:"rule_type"`
	ObjectLabel string  `json:"object_label,omitempty"`
	Confidence  float64 `json:"confidence,omitempty"`
	SnapshotURL string  `json:"snapshot_url,omitempty"`
	ClipURL     string  `json:"clip_url,omitempty"`
	DurationMs  int64   `json:"duration_ms,omitempty"`
}

func (s *Server) alarmsPath() string {
	return filepath.Join(s.baseDir, "logs", "alarms.jsonl")
}

// handleAlarmReport receives alarm notifications from media-server.
// POST /v1/alarms/report
func (s *Server) handleAlarmReport(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		errorJSON(w, http.StatusMethodNotAllowed, "method not allowed")
		return
	}
	if !s.authorize(r, true) {
		errorJSON(w, http.StatusUnauthorized, "unauthorized")
		return
	}

	maxBytes := int64(1 << 20) // 1MB max
	r.Body = http.MaxBytesReader(w, r.Body, maxBytes)

	var alarm alarmRecord
	if err := json.NewDecoder(r.Body).Decode(&alarm); err != nil {
		errorJSON(w, http.StatusBadRequest, "invalid json: "+err.Error())
		return
	}
	if strings.TrimSpace(alarm.Channel) == "" {
		errorJSON(w, http.StatusBadRequest, "channel is required")
		return
	}
	if strings.TrimSpace(alarm.RuleName) == "" {
		errorJSON(w, http.StatusBadRequest, "rule_name is required")
		return
	}
	if alarm.ID == "" {
		alarm.ID = fmt.Sprintf("alarm_%s_%s", time.Now().Format("20060102_150405"), randomHex(6))
	}
	if alarm.Timestamp == "" {
		alarm.Timestamp = time.Now().Format(time.RFC3339)
	}

	path := s.alarmsPath()
	dir := filepath.Dir(path)
	if err := files.EnsureDir(dir, 0o755); err != nil {
		errorJSON(w, http.StatusInternalServerError, "internal error: "+err.Error())
		return
	}

	line, err := json.Marshal(alarm)
	if err != nil {
		errorJSON(w, http.StatusInternalServerError, "internal error: "+err.Error())
		return
	}

	f, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o644)
	if err != nil {
		errorJSON(w, http.StatusInternalServerError, "internal error: "+err.Error())
		return
	}
	defer f.Close()

	if _, err := fmt.Fprintf(f, "%s\n", string(line)); err != nil {
		errorJSON(w, http.StatusInternalServerError, "internal error: "+err.Error())
		return
	}

	s.recordAudit(r, "alarm.report", true, alarm.ID)
	writeJSON(w, http.StatusOK, map[string]any{"ok": true, "id": alarm.ID})
}

// handleAlarmsRecent returns recent alarm records.
// GET /v1/alarms/recent?limit=50&since=2026-01-01T00:00:00Z
func (s *Server) handleAlarmsRecent(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		errorJSON(w, http.StatusMethodNotAllowed, "method not allowed")
		return
	}
	if !s.authorize(r, false) {
		errorJSON(w, http.StatusUnauthorized, "unauthorized")
		return
	}

	limit := 50
	if v := strings.TrimSpace(r.URL.Query().Get("limit")); v != "" {
		if n, err := strconv.Atoi(v); err == nil && n > 0 && n <= 500 {
			limit = n
		}
	}

	alarms, err := s.readRecentAlarms(limit)
	if err != nil {
		errorJSON(w, http.StatusInternalServerError, "internal error: "+err.Error())
		return
	}
	if alarms == nil {
		alarms = make([]alarmRecord, 0)
	}

	writeJSON(w, http.StatusOK, map[string]any{"alarms": alarms})
}

func (s *Server) readRecentAlarms(limit int) ([]alarmRecord, error) {
	path := s.alarmsPath()
	f, err := os.Open(path)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, err
	}
	defer f.Close()

	// Read all lines and keep last N
	var lines []string
	scanner := bufio.NewScanner(f)
	scanner.Buffer(make([]byte, 1<<20), 1<<20) // 1MB max line
	for scanner.Scan() {
		line := scanner.Text()
		if strings.TrimSpace(line) == "" {
			continue
		}
		lines = append(lines, line)
		// Keep only last 2*limit lines in memory
		if len(lines) > 2*limit {
			lines = lines[limit:]
		}
	}
	if err := scanner.Err(); err != nil && err != io.EOF {
		return nil, err
	}

	// Take last `limit` lines
	start := 0
	if len(lines) > limit {
		start = len(lines) - limit
	}

	alarms := make([]alarmRecord, 0, limit)
	for i := start; i < len(lines); i++ {
		var alarm alarmRecord
		if err := json.Unmarshal([]byte(lines[i]), &alarm); err != nil {
			continue // skip malformed lines
		}
		alarms = append(alarms, alarm)
	}
	return alarms, nil
}

func randomHex(n int) string {
	b := make([]byte, n)
	rand.Read(b)
	return hex.EncodeToString(b)[:n]
}