package webui

import (
	"bufio"
	"io"
	"log/slog"
	"os"
	"strings"
	"sync"
	"time"

	"bee/audit/internal/app"
	"bee/audit/internal/platform"
)

// kmsgWatcher reads /dev/kmsg and accumulates hardware error events.
// It supports multiple concurrent SAT tasks: a shared event window is open
// while any SAT task is running, and flushed when all tasks complete.
type kmsgWatcher struct {
	mu          sync.Mutex
	activeCount int // number of in-flight SAT tasks
	window      *kmsgWindow
	statusDB    *app.ComponentStatusDB
}

type kmsgWindow struct {
	targets   []string // SAT targets running concurrently
	startedAt time.Time
	seen      map[kmsgEventKey]bool
	events    []kmsgEvent
}

type kmsgEventKey struct {
	id       string // BDF or device name
	category string
}

type kmsgEvent struct {
	timestamp time.Time
	raw       string
	ids       []string // BDF addresses or device names extracted
	category  string
}

func newKmsgWatcher(statusDB *app.ComponentStatusDB) *kmsgWatcher {
	return &kmsgWatcher{statusDB: statusDB}
}

// start launches the background kmsg reading goroutine.
func (w *kmsgWatcher) start() {
	goRecoverLoop("kmsg watcher", 5*time.Second, w.run)
}

func (w *kmsgWatcher) run() {
	for {
		f, err := os.Open("/dev/kmsg")
		if err != nil {
			slog.Warn("kmsg watcher unavailable", "err", err)
			time.Sleep(30 * time.Second)
			continue
		}
		// Best-effort seek to end so we only capture events from now forward.
		_, _ = f.Seek(0, io.SeekEnd)

		scanner := bufio.NewScanner(f)
		scanner.Buffer(make([]byte, 64*1024), 64*1024)
		for scanner.Scan() {
			line := scanner.Text()
			evt, ok := parseKmsgLine(line)
			if !ok {
				continue
			}
			w.mu.Lock()
			if w.window != nil {
				w.recordEvent(evt)
			}
			w.mu.Unlock()
		}
		if err := scanner.Err(); err != nil {
			slog.Warn("kmsg watcher stopped", "err", err)
		}
		_ = f.Close()
		time.Sleep(2 * time.Second)
	}
}

// recordEvent appends evt to the active window, deduplicating by (id, category).
// Must be called with w.mu held.
func (w *kmsgWatcher) recordEvent(evt kmsgEvent) {
	if len(evt.ids) == 0 {
		key := kmsgEventKey{id: "", category: evt.category}
		if !w.window.seen[key] {
			w.window.seen[key] = true
			w.window.events = append(w.window.events, evt)
		}
		return
	}
	for _, id := range evt.ids {
		key := kmsgEventKey{id: id, category: evt.category}
		if !w.window.seen[key] {
			w.window.seen[key] = true
			w.window.events = append(w.window.events, evt)
		}
	}
}

// NotifyTaskStarted increments the active task counter and opens a shared event window
// if this is the first task starting.
func (w *kmsgWatcher) NotifyTaskStarted(taskID, target string) {
	w.mu.Lock()
	defer w.mu.Unlock()
	if w.activeCount == 0 {
		w.window = &kmsgWindow{
			startedAt: time.Now(),
			seen:      make(map[kmsgEventKey]bool),
		}
	}
	w.activeCount++
	if w.window != nil {
		w.window.targets = append(w.window.targets, target)
	}
}

// NotifyTaskFinished decrements the active task counter. When all tasks finish,
// it flushes the accumulated events to the status DB.
func (w *kmsgWatcher) NotifyTaskFinished(taskID string) {
	w.mu.Lock()
	w.activeCount--
	var window *kmsgWindow
	if w.activeCount <= 0 {
		w.activeCount = 0
		window = w.window
		w.window = nil
	}
	w.mu.Unlock()

	if window == nil || len(window.events) == 0 {
		return
	}
	goRecoverOnce("kmsg watcher flush", func() { w.flushWindow(window) })
}

func (w *kmsgWatcher) flushWindow(window *kmsgWindow) {
	if w.statusDB == nil {
		return
	}
	source := "watchdog:kmsg"
	// Collect unique component keys from events.
	seen := map[string]string{} // componentKey → first raw line
	for _, evt := range window.events {
		if len(evt.ids) == 0 {
			// MCE or un-identified error.
			key := "cpu:all"
			if evt.category == "memory" {
				key = "memory:all"
			}
			if _, exists := seen[key]; !exists {
				seen[key] = evt.raw
			}
			continue
		}
		for _, id := range evt.ids {
			var key string
			switch evt.category {
			case "gpu", "pcie":
				key = "pcie:" + normalizeBDF(id)
			case "storage":
				key = "storage:" + id
			default:
				key = "pcie:" + normalizeBDF(id)
			}
			if _, exists := seen[key]; !exists {
				seen[key] = evt.raw
			}
		}
	}
	for key, detail := range seen {
		detail = "kernel error during SAT (" + strings.Join(window.targets, ",") + "): " + truncate(detail, 120)
		w.statusDB.Record(key, source, "Warning", detail)
	}
}

// parseKmsgLine parses a single /dev/kmsg line and returns an event if it matches
// any pattern in platform.HardwareErrorPatterns.
// kmsg format: "<priority>,<sequence>,<timestamp_usec>,-;message text"
func parseKmsgLine(raw string) (kmsgEvent, bool) {
	msg := raw
	if idx := strings.Index(raw, ";"); idx >= 0 {
		msg = strings.TrimSpace(raw[idx+1:])
	}
	if msg == "" {
		return kmsgEvent{}, false
	}

	for _, p := range platform.HardwareErrorPatterns {
		m := p.Re.FindStringSubmatch(msg)
		if m == nil {
			continue
		}
		evt := kmsgEvent{
			timestamp: time.Now(),
			raw:       msg,
			category:  p.Category,
		}
		if p.BDFGroup > 0 && p.BDFGroup < len(m) {
			evt.ids = append(evt.ids, normalizeBDF(m[p.BDFGroup]))
		}
		if p.DevGroup > 0 && p.DevGroup < len(m) {
			evt.ids = append(evt.ids, m[p.DevGroup])
		}
		return evt, true
	}
	return kmsgEvent{}, false
}

// normalizeBDF normalizes a PCIe BDF to the 4-part form "0000:c8:00.0".
func normalizeBDF(bdf string) string {
	bdf = strings.ToLower(strings.TrimSpace(bdf))
	if strings.Count(bdf, ":") == 1 {
		return "0000:" + bdf
	}
	return bdf
}

func truncate(s string, max int) string {
	if len(s) <= max {
		return s
	}
	return s[:max] + "..."
}

// isSATTarget returns true for task targets that run hardware acceptance tests.
func isSATTarget(target string) bool {
	switch target {
	case "nvidia", "nvidia-targeted-stress", "nvidia-benchmark", "nvidia-compute", "nvidia-targeted-power", "nvidia-pulse",
		"nvidia-interconnect", "nvidia-bandwidth", "nvidia-stress", "memory", "memory-stress", "storage",
		"cpu", "sat-stress", "amd", "amd-mem", "amd-bandwidth", "amd-stress",
		"platform-stress":
		return true
	}
	return false
}