package webui

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"sync"
	"time"

	"bee/audit/internal/app"
)

// Task statuses.
const (
	TaskPending   = "pending"
	TaskRunning   = "running"
	TaskDone      = "done"
	TaskFailed    = "failed"
	TaskCancelled = "cancelled"
)

// taskNames maps target → human-readable name.
var taskNames = map[string]string{
	"nvidia":         "NVIDIA SAT",
	"memory":         "Memory SAT",
	"storage":        "Storage SAT",
	"cpu":            "CPU SAT",
	"amd":            "AMD GPU SAT",
	"amd-stress":     "AMD GPU Burn-in",
	"memory-stress":  "Memory Burn-in",
	"sat-stress":     "SAT Stress (stressapptest)",
	"audit":          "Audit",
	"install":        "Install to Disk",
	"install-to-ram": "Install to RAM",
}

// Task represents one unit of work in the queue.
type Task struct {
	ID        string     `json:"id"`
	Name      string     `json:"name"`
	Target    string     `json:"target"`
	Priority  int        `json:"priority"`
	Status    string     `json:"status"`
	CreatedAt time.Time  `json:"created_at"`
	StartedAt *time.Time `json:"started_at,omitempty"`
	DoneAt    *time.Time `json:"done_at,omitempty"`
	ErrMsg    string     `json:"error,omitempty"`
	LogPath   string     `json:"log_path,omitempty"`

	// runtime fields (not serialised)
	job    *jobState
	params taskParams
}

// taskParams holds optional parameters parsed from the run request.
type taskParams struct {
	Duration    int    `json:"duration,omitempty"`
	DiagLevel   int    `json:"diag_level,omitempty"`
	GPUIndices  []int  `json:"gpu_indices,omitempty"`
	BurnProfile string `json:"burn_profile,omitempty"`
	DisplayName string `json:"display_name,omitempty"`
	Device      string `json:"device,omitempty"` // for install
}

type persistedTask struct {
	ID        string     `json:"id"`
	Name      string     `json:"name"`
	Target    string     `json:"target"`
	Priority  int        `json:"priority"`
	Status    string     `json:"status"`
	CreatedAt time.Time  `json:"created_at"`
	StartedAt *time.Time `json:"started_at,omitempty"`
	DoneAt    *time.Time `json:"done_at,omitempty"`
	ErrMsg    string     `json:"error,omitempty"`
	LogPath   string     `json:"log_path,omitempty"`
	Params    taskParams `json:"params,omitempty"`
}

type burnPreset struct {
	NvidiaDiag  int
	DurationSec int
}

func resolveBurnPreset(profile string) burnPreset {
	switch profile {
	case "overnight":
		return burnPreset{NvidiaDiag: 4, DurationSec: 8 * 60 * 60}
	case "acceptance":
		return burnPreset{NvidiaDiag: 3, DurationSec: 60 * 60}
	default:
		return burnPreset{NvidiaDiag: 1, DurationSec: 5 * 60}
	}
}

// taskQueue manages a priority-ordered list of tasks and runs them one at a time.
type taskQueue struct {
	mu        sync.Mutex
	tasks     []*Task
	trigger   chan struct{}
	opts      *HandlerOptions // set by startWorker
	statePath string
	logsDir   string
	started   bool
}

var globalQueue = &taskQueue{trigger: make(chan struct{}, 1)}

const maxTaskHistory = 50

var (
	runMemoryAcceptancePackCtx = func(a *app.App, ctx context.Context, baseDir string, logFunc func(string)) (string, error) {
		return a.RunMemoryAcceptancePackCtx(ctx, baseDir, logFunc)
	}
	runStorageAcceptancePackCtx = func(a *app.App, ctx context.Context, baseDir string, logFunc func(string)) (string, error) {
		return a.RunStorageAcceptancePackCtx(ctx, baseDir, logFunc)
	}
	runCPUAcceptancePackCtx = func(a *app.App, ctx context.Context, baseDir string, durationSec int, logFunc func(string)) (string, error) {
		return a.RunCPUAcceptancePackCtx(ctx, baseDir, durationSec, logFunc)
	}
	runAMDAcceptancePackCtx = func(a *app.App, ctx context.Context, baseDir string, logFunc func(string)) (string, error) {
		return a.RunAMDAcceptancePackCtx(ctx, baseDir, logFunc)
	}
	runAMDStressPackCtx = func(a *app.App, ctx context.Context, baseDir string, durationSec int, logFunc func(string)) (string, error) {
		return a.RunAMDStressPackCtx(ctx, baseDir, durationSec, logFunc)
	}
	runMemoryStressPackCtx = func(a *app.App, ctx context.Context, baseDir string, durationSec int, logFunc func(string)) (string, error) {
		return a.RunMemoryStressPackCtx(ctx, baseDir, durationSec, logFunc)
	}
	runSATStressPackCtx = func(a *app.App, ctx context.Context, baseDir string, durationSec int, logFunc func(string)) (string, error) {
		return a.RunSATStressPackCtx(ctx, baseDir, durationSec, logFunc)
	}
)

// enqueue adds a task to the queue and notifies the worker.
func (q *taskQueue) enqueue(t *Task) {
	q.mu.Lock()
	q.assignTaskLogPathLocked(t)
	q.tasks = append(q.tasks, t)
	q.prune()
	q.persistLocked()
	q.mu.Unlock()
	select {
	case q.trigger <- struct{}{}:
	default:
	}
}

// prune removes oldest completed tasks beyond maxTaskHistory.
func (q *taskQueue) prune() {
	var done []*Task
	var active []*Task
	for _, t := range q.tasks {
		switch t.Status {
		case TaskDone, TaskFailed, TaskCancelled:
			done = append(done, t)
		default:
			active = append(active, t)
		}
	}
	if len(done) > maxTaskHistory {
		done = done[len(done)-maxTaskHistory:]
	}
	q.tasks = append(active, done...)
}

// nextPending returns the highest-priority pending task (nil if none).
func (q *taskQueue) nextPending() *Task {
	var best *Task
	for _, t := range q.tasks {
		if t.Status != TaskPending {
			continue
		}
		if best == nil || t.Priority > best.Priority ||
			(t.Priority == best.Priority && t.CreatedAt.Before(best.CreatedAt)) {
			best = t
		}
	}
	return best
}

// findByID looks up a task by ID.
func (q *taskQueue) findByID(id string) (*Task, bool) {
	q.mu.Lock()
	defer q.mu.Unlock()
	for _, t := range q.tasks {
		if t.ID == id {
			return t, true
		}
	}
	return nil, false
}

// findJob returns the jobState for a task ID (for SSE streaming compatibility).
func (q *taskQueue) findJob(id string) (*jobState, bool) {
	t, ok := q.findByID(id)
	if !ok || t.job == nil {
		return nil, false
	}
	return t.job, true
}

func (q *taskQueue) hasActiveTarget(target string) bool {
	q.mu.Lock()
	defer q.mu.Unlock()
	for _, t := range q.tasks {
		if t.Target != target {
			continue
		}
		if t.Status == TaskPending || t.Status == TaskRunning {
			return true
		}
	}
	return false
}

// snapshot returns a copy of all tasks sorted for display (running first, then pending by priority, then done by doneAt desc).
func (q *taskQueue) snapshot() []Task {
	q.mu.Lock()
	defer q.mu.Unlock()
	out := make([]Task, len(q.tasks))
	for i, t := range q.tasks {
		out[i] = *t
	}
	sort.SliceStable(out, func(i, j int) bool {
		si := statusOrder(out[i].Status)
		sj := statusOrder(out[j].Status)
		if si != sj {
			return si < sj
		}
		if out[i].Priority != out[j].Priority {
			return out[i].Priority > out[j].Priority
		}
		return out[i].CreatedAt.Before(out[j].CreatedAt)
	})
	return out
}

func statusOrder(s string) int {
	switch s {
	case TaskRunning:
		return 0
	case TaskPending:
		return 1
	default:
		return 2
	}
}

// startWorker launches the queue runner goroutine.
func (q *taskQueue) startWorker(opts *HandlerOptions) {
	q.mu.Lock()
	q.opts = opts
	q.statePath = filepath.Join(opts.ExportDir, "tasks-state.json")
	q.logsDir = filepath.Join(opts.ExportDir, "tasks")
	_ = os.MkdirAll(q.logsDir, 0755)
	if !q.started {
		q.loadLocked()
		q.started = true
		go q.worker()
	}
	hasPending := q.nextPending() != nil
	q.mu.Unlock()
	if hasPending {
		select {
		case q.trigger <- struct{}{}:
		default:
		}
	}
}

func (q *taskQueue) worker() {
	for {
		<-q.trigger
		setCPUGovernor("performance")
		for {
			q.mu.Lock()
			t := q.nextPending()
			if t == nil {
				q.mu.Unlock()
				break
			}
			now := time.Now()
			t.Status = TaskRunning
			t.StartedAt = &now
			t.DoneAt = nil
			t.ErrMsg = ""
			j := newTaskJobState(t.LogPath)
			ctx, cancel := context.WithCancel(context.Background())
			j.cancel = cancel
			t.job = j
			q.persistLocked()
			q.mu.Unlock()

			q.runTask(t, j, ctx)

			q.mu.Lock()
			now2 := time.Now()
			t.DoneAt = &now2
			if t.Status == TaskRunning { // not cancelled externally
				if j.err != "" {
					t.Status = TaskFailed
					t.ErrMsg = j.err
				} else {
					t.Status = TaskDone
				}
			}
			q.prune()
			q.persistLocked()
			q.mu.Unlock()
		}
		setCPUGovernor("powersave")
	}
}

// setCPUGovernor writes the given governor to all CPU scaling_governor sysfs files.
// Silently ignores errors (e.g. when cpufreq is not available).
func setCPUGovernor(governor string) {
	matches, err := filepath.Glob("/sys/devices/system/cpu/cpu*/cpufreq/scaling_governor")
	if err != nil || len(matches) == 0 {
		return
	}
	for _, path := range matches {
		_ = os.WriteFile(path, []byte(governor), 0644)
	}
}

// runTask executes the work for a task, writing output to j.
func (q *taskQueue) runTask(t *Task, j *jobState, ctx context.Context) {
	if q.opts == nil || q.opts.App == nil {
		j.append("ERROR: app not configured")
		j.finish("app not configured")
		return
	}
	a := q.opts.App

	j.append(fmt.Sprintf("Starting %s...", t.Name))
	if len(j.lines) > 0 {
		j.append(fmt.Sprintf("Recovered after bee-web restart at %s", time.Now().UTC().Format(time.RFC3339)))
	}

	var (
		archive string
		err     error
	)

	switch t.Target {
	case "nvidia":
		diagLevel := t.params.DiagLevel
		if t.params.BurnProfile != "" && diagLevel <= 0 {
			diagLevel = resolveBurnPreset(t.params.BurnProfile).NvidiaDiag
		}
		if len(t.params.GPUIndices) > 0 || diagLevel > 0 {
			result, e := a.RunNvidiaAcceptancePackWithOptions(
				ctx, "", diagLevel, t.params.GPUIndices, j.append,
			)
			if e != nil {
				err = e
			} else {
				archive = result.Body
			}
		} else {
			archive, err = a.RunNvidiaAcceptancePack("", j.append)
		}
	case "memory":
		archive, err = runMemoryAcceptancePackCtx(a, ctx, "", j.append)
	case "storage":
		archive, err = runStorageAcceptancePackCtx(a, ctx, "", j.append)
	case "cpu":
		dur := t.params.Duration
		if t.params.BurnProfile != "" && dur <= 0 {
			dur = resolveBurnPreset(t.params.BurnProfile).DurationSec
		}
		if dur <= 0 {
			dur = 60
		}
		archive, err = runCPUAcceptancePackCtx(a, ctx, "", dur, j.append)
	case "amd":
		archive, err = runAMDAcceptancePackCtx(a, ctx, "", j.append)
	case "amd-stress":
		dur := t.params.Duration
		if t.params.BurnProfile != "" && dur <= 0 {
			dur = resolveBurnPreset(t.params.BurnProfile).DurationSec
		}
		archive, err = runAMDStressPackCtx(a, ctx, "", dur, j.append)
	case "memory-stress":
		dur := t.params.Duration
		if t.params.BurnProfile != "" && dur <= 0 {
			dur = resolveBurnPreset(t.params.BurnProfile).DurationSec
		}
		archive, err = runMemoryStressPackCtx(a, ctx, "", dur, j.append)
	case "sat-stress":
		dur := t.params.Duration
		if t.params.BurnProfile != "" && dur <= 0 {
			dur = resolveBurnPreset(t.params.BurnProfile).DurationSec
		}
		archive, err = runSATStressPackCtx(a, ctx, "", dur, j.append)
	case "audit":
		result, e := a.RunAuditNow(q.opts.RuntimeMode)
		if e != nil {
			err = e
		} else {
			for _, line := range splitLines(result.Body) {
				j.append(line)
			}
		}
	case "install-to-ram":
		err = a.RunInstallToRAM(ctx, j.append)
	default:
		j.append("ERROR: unknown target: " + t.Target)
		j.finish("unknown target")
		return
	}

	if err != nil {
		if ctx.Err() != nil {
			j.append("Aborted.")
			j.finish("aborted")
		} else {
			j.append("ERROR: " + err.Error())
			j.finish(err.Error())
		}
		return
	}
	if archive != "" {
		j.append("Archive: " + archive)
	}
	j.finish("")
}

func splitLines(s string) []string {
	var out []string
	for _, l := range splitNL(s) {
		if l != "" {
			out = append(out, l)
		}
	}
	return out
}

func splitNL(s string) []string {
	var out []string
	start := 0
	for i, c := range s {
		if c == '\n' {
			out = append(out, s[start:i])
			start = i + 1
		}
	}
	out = append(out, s[start:])
	return out
}

// ── HTTP handlers ─────────────────────────────────────────────────────────────

func (h *handler) handleAPITasksList(w http.ResponseWriter, _ *http.Request) {
	tasks := globalQueue.snapshot()
	writeJSON(w, tasks)
}

func (h *handler) handleAPITasksCancel(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	t, ok := globalQueue.findByID(id)
	if !ok {
		writeError(w, http.StatusNotFound, "task not found")
		return
	}
	globalQueue.mu.Lock()
	defer globalQueue.mu.Unlock()
	switch t.Status {
	case TaskPending:
		t.Status = TaskCancelled
		now := time.Now()
		t.DoneAt = &now
		globalQueue.persistLocked()
		writeJSON(w, map[string]string{"status": "cancelled"})
	case TaskRunning:
		if t.job != nil {
			t.job.abort()
		}
		t.Status = TaskCancelled
		now := time.Now()
		t.DoneAt = &now
		globalQueue.persistLocked()
		writeJSON(w, map[string]string{"status": "cancelled"})
	default:
		writeError(w, http.StatusConflict, "task is not running or pending")
	}
}

func (h *handler) handleAPITasksPriority(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	t, ok := globalQueue.findByID(id)
	if !ok {
		writeError(w, http.StatusNotFound, "task not found")
		return
	}
	var req struct {
		Delta int `json:"delta"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid body")
		return
	}
	globalQueue.mu.Lock()
	defer globalQueue.mu.Unlock()
	if t.Status != TaskPending {
		writeError(w, http.StatusConflict, "only pending tasks can be reprioritised")
		return
	}
	t.Priority += req.Delta
	globalQueue.persistLocked()
	writeJSON(w, map[string]int{"priority": t.Priority})
}

func (h *handler) handleAPITasksCancelAll(w http.ResponseWriter, _ *http.Request) {
	globalQueue.mu.Lock()
	now := time.Now()
	n := 0
	for _, t := range globalQueue.tasks {
		switch t.Status {
		case TaskPending:
			t.Status = TaskCancelled
			t.DoneAt = &now
			n++
		case TaskRunning:
			if t.job != nil {
				t.job.abort()
			}
			t.Status = TaskCancelled
			t.DoneAt = &now
			n++
		}
	}
	globalQueue.persistLocked()
	globalQueue.mu.Unlock()
	writeJSON(w, map[string]int{"cancelled": n})
}

func (h *handler) handleAPITasksStream(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	// Wait up to 5s for the task to get a job (it may be pending)
	deadline := time.Now().Add(5 * time.Second)
	var j *jobState
	for time.Now().Before(deadline) {
		if jj, ok := globalQueue.findJob(id); ok {
			j = jj
			break
		}
		time.Sleep(200 * time.Millisecond)
	}
	if j == nil {
		http.Error(w, "task not found or not yet started", http.StatusNotFound)
		return
	}
	streamJob(w, r, j)
}

func (q *taskQueue) assignTaskLogPathLocked(t *Task) {
	if t.LogPath != "" || q.logsDir == "" || t.ID == "" {
		return
	}
	t.LogPath = filepath.Join(q.logsDir, t.ID+".log")
}

func (q *taskQueue) loadLocked() {
	if q.statePath == "" {
		return
	}
	data, err := os.ReadFile(q.statePath)
	if err != nil || len(data) == 0 {
		return
	}
	var persisted []persistedTask
	if err := json.Unmarshal(data, &persisted); err != nil {
		return
	}
	for _, pt := range persisted {
		t := &Task{
			ID:        pt.ID,
			Name:      pt.Name,
			Target:    pt.Target,
			Priority:  pt.Priority,
			Status:    pt.Status,
			CreatedAt: pt.CreatedAt,
			StartedAt: pt.StartedAt,
			DoneAt:    pt.DoneAt,
			ErrMsg:    pt.ErrMsg,
			LogPath:   pt.LogPath,
			params:    pt.Params,
		}
		q.assignTaskLogPathLocked(t)
		if t.Status == TaskPending || t.Status == TaskRunning {
			t.Status = TaskPending
			t.DoneAt = nil
			t.ErrMsg = ""
		}
		q.tasks = append(q.tasks, t)
	}
	q.prune()
	q.persistLocked()
}

func (q *taskQueue) persistLocked() {
	if q.statePath == "" {
		return
	}
	state := make([]persistedTask, 0, len(q.tasks))
	for _, t := range q.tasks {
		state = append(state, persistedTask{
			ID:        t.ID,
			Name:      t.Name,
			Target:    t.Target,
			Priority:  t.Priority,
			Status:    t.Status,
			CreatedAt: t.CreatedAt,
			StartedAt: t.StartedAt,
			DoneAt:    t.DoneAt,
			ErrMsg:    t.ErrMsg,
			LogPath:   t.LogPath,
			Params:    t.params,
		})
	}
	data, err := json.MarshalIndent(state, "", "  ")
	if err != nil {
		return
	}
	tmp := q.statePath + ".tmp"
	if err := os.WriteFile(tmp, data, 0644); err != nil {
		return
	}
	_ = os.Rename(tmp, q.statePath)
}