package seed

import (
	"context"
	"fmt"
	"math/rand"
	"time"

	"github.com/x0gp/server/internal/clans"
	"github.com/x0gp/server/internal/drivers"
	"github.com/x0gp/server/internal/lobby"
	"github.com/x0gp/server/internal/races"
)

// DefaultCounts are the volumes produced by Run.
type DefaultCounts struct {
	Finished int // default 30
	Live     int // default 5
	Plans    int // default 5
}

// DefaultSeed is the deterministic seed.
const DefaultSeed = 0xA1B2C3D4

// DefaultNow is overridable for tests.
var DefaultNow = time.Now

// Track catalogue used by the seeder. Loaded from the tracks table at
// run time. If no tracks exist, the seeder falls back to ["default"].
var fallbackTracks = []string{"default"}

var defaultDriverSeeds = []struct {
	nick string
	name string
}{
	{"ACE", "Alice"},
	{"BOB", "Bob"},
	{"CAR", "Carol"},
	{"DAV", "Dave"},
	{"EVE", "Eve"},
	{"FRA", "Frank"},
	{"GRA", "Grace"},
	{"HEI", "Heidi"},
	{"IVY", "Ivy"},
	{"JAC", "Jack"},
	{"KEN", "Ken"},
	{"LEO", "Leo"},
	{"MAX", "Max"},
	{"NED", "Ned"},
	{"OLI", "Oliver"},
	{"PEP", "Peggy"},
	{"QIN", "Quincy"},
	{"ROY", "Roy"},
	{"SAM", "Sam"},
	{"TED", "Ted"},
}

// Default clans.
var defaultClanSeeds = []struct {
	tag  string
	name string
}{
	{"ACE", "Ace Racing"},
	{"RND", "Rounders"},
	{"SPD", "Speed Demons"},
}

// Options configures Run.
type Options struct {
	Counts DefaultCounts
	Seed   int64
	Reset  bool
	Now    time.Time
}

// Summary is the result of Run.
type Summary struct {
	FinishedInserted int
	LiveCreated      int
	PlansInserted    int
	QueueInserted    int
	Duration         time.Duration
}

// Runner is a self-contained seeder wired to the package's pg store and
// lobby. Hold one per process; safe to call Run multiple times.
type Runner struct {
	pg        *races.PgStore
	lb        *lobby.Service
	live      *races.LiveStore
	clansPg   *clans.PgStore
	driversPg *drivers.PgStore
	opt       Options
	rng       *rand.Rand
	now       time.Time

	// Filled by loadInputs.
	trackIDs   []string
	driverIDs  []string // driver ids in the order they exist after seed
	driverInfo []seedDriver // id, nick, name, clanID, clanTag
	clanByID   map[string]string // clan id -> tag (for fast profile updates)
}

type seedDriver struct {
	ID       string
	Nickname string
	Name     string
	ClanID   string
	ClanTag  string
}

// NewRunner constructs a Runner.
func NewRunner(pg *races.PgStore, lb *lobby.Service, live *races.LiveStore, clansPg *clans.PgStore, driversPg *drivers.PgStore) *Runner {
	return &Runner{pg: pg, lb: lb, live: live, clansPg: clansPg, driversPg: driversPg}
}

// Run executes the seed against the supplied services.
//
// Order of operations:
//
//  1. (optional) reset: TRUNCATE finished_races, race_plans, race_queue;
//     remove all live races from the lobby; remove the auto-seeded drivers
//     from the lobby.
//  2. Insert N finished races into Postgres. These do NOT touch the lobby.
//  3. Create M live races in the lobby (mix of statuses).
//  4. Insert K race plans into Postgres. The scheduler will materialise
//     them on its next tick (start_at_ms is in the future).
//  5. Enqueue the first two drivers for the next 2 live races.
func (r *Runner) Run(ctx context.Context, opt Options) (Summary, error) {
	if opt.Seed == 0 {
		opt.Seed = DefaultSeed
	}
	if opt.Now.IsZero() {
		opt.Now = DefaultNow()
	}
	if opt.Counts.Finished == 0 {
		opt.Counts.Finished = 30
	}
	if opt.Counts.Live == 0 {
		opt.Counts.Live = 5
	}
	if opt.Counts.Plans == 0 {
		opt.Counts.Plans = 5
	}

	start := time.Now()
	var s Summary

	if opt.Reset {
		if err := r.resetAll(ctx); err != nil {
			return s, fmt.Errorf("reset: %w", err)
		}
	}

	r.rng = rand.New(rand.NewSource(opt.Seed))
	r.now = opt.Now

	// 0. Seed drivers and clans (idempotent). Then load real track ids
	// from the catalog so race_plans / finished_races only reference
	// tracks that actually exist in the DB.
	if err := r.seedDriversAndClans(ctx); err != nil {
		return s, fmt.Errorf("seed drivers/clans: %w", err)
	}
	if err := r.loadTracks(ctx); err != nil {
		return s, fmt.Errorf("load tracks: %w", err)
	}
	if err := r.loadDrivers(ctx); err != nil {
		return s, fmt.Errorf("load drivers: %w", err)
	}

	// 1. Finished races.
	for i := 0; i < opt.Counts.Finished; i++ {
		row := r.makeFinished(i)
		if err := r.pg.InsertFinished(ctx, row); err != nil {
			return s, fmt.Errorf("insert finished %d: %w", i, err)
		}
		s.FinishedInserted++
	}

	// 2. Live races in the lobby.
	statuses := []lobby.RaceStatus{
		lobby.RaceStatusLobby,
		lobby.RaceStatusLobby,
		lobby.RaceStatusCountdown,
		lobby.RaceStatusRacing,
		lobby.RaceStatusLobby,
	}
	for i := 0; i < opt.Counts.Live && i < len(statuses); i++ {
		meta, err := r.createLive(statuses[i], i)
		if err != nil {
			return s, fmt.Errorf("create live %d: %w", i, err)
		}
		if statuses[i] != lobby.RaceStatusLobby {
			if err := r.lb.SetRaceStatus(meta.ID, statuses[i]); err != nil {
				return s, fmt.Errorf("set status %s: %w", meta.ID, err)
			}
			// Flush the new status synchronously so the DB row is in
			// sync with in-memory (mirror goroutines may not have run
			// yet).
			if r.live != nil {
				flushCtx, flushCancel := context.WithTimeout(ctx, 2*time.Second)
				cur, err := r.lb.GetRace(meta.ID)
				if err == nil {
					_ = r.live.SetRaceStatus(flushCtx, cur.ID, cur.Status, cur.StartedMs)
				}
				flushCancel()
			}
		}
		s.LiveCreated++

		// First two live races: enqueue first two drivers on this race.
		if i < 2 {
			for _, d := range r.driverInfo[:2] {
				if _, err := r.pg.Enqueue(ctx, d.ID, meta.ID, ""); err != nil {
					return s, fmt.Errorf("enqueue %s: %w", d.ID, err)
				}
				s.QueueInserted++
			}
		}
	}

	// 3. Race plans. Mix of one-shot and recurring.
	planShapes := []planShape{
		{intervalS: 0, offsetS: 5 * 60},     // one-shot in 5 min
		{intervalS: 60, offsetS: 30 * 60},   // every minute, start in 30 min
		{intervalS: 3600, count: 24, offsetS: 60 * 60},  // hourly x24, start in 1h
		{intervalS: 0, offsetS: 6 * 3600},   // one-shot in 6h
		{intervalS: 86400, offsetS: 24 * 3600}, // daily, start tomorrow
	}
	for i := 0; i < opt.Counts.Plans && i < len(planShapes); i++ {
		ps := planShapes[i]
		p := r.makePlan(i, ps)
		if err := r.pg.CreatePlan(ctx, p); err != nil {
			return s, fmt.Errorf("create plan %d: %w", i, err)
		}
		s.PlansInserted++
	}

	if err := r.seedTrackCalendar(ctx); err != nil {
		return s, fmt.Errorf("seed track calendar: %w", err)
	}

	s.Duration = time.Since(start)
	return s, nil
}

func (r *Runner) seedTrackCalendar(ctx context.Context) error {
	now := r.now
	
	if len(r.trackIDs) == 0 {
		return nil
	}

	tracksMap := make(map[string]bool)
	for _, id := range r.trackIDs {
		tracksMap[id] = true
	}

	schedule := []struct {
		trackID string
		startAt time.Time
		endAt   time.Time
	}{
		{"monaco", now.Add(-14 * 24 * time.Hour), now.Add(-7 * 24 * time.Hour)},
		{"barcelona-catalunya", now.Add(-2 * 24 * time.Hour), now.Add(12 * 24 * time.Hour)},
		{"austria-redbull-ring", now.Add(14 * 24 * time.Hour), now.Add(28 * 24 * time.Hour)},
		{"great-britain-silverstone", now.Add(28 * 24 * time.Hour), now.Add(42 * 24 * time.Hour)},
		{"belgium-spa", now.Add(42 * 24 * time.Hour), now.Add(56 * 24 * time.Hour)},
	}

	for _, s := range schedule {
		if !tracksMap[s.trackID] {
			continue
		}
		_, err := r.pg.Exec(ctx, `
			INSERT INTO track_calendar (track_id, start_at, end_at)
			VALUES ($1, $2, $3)
		`, s.trackID, s.startAt, s.endAt)
		if err != nil {
			return fmt.Errorf("insert calendar entry: %w", err)
		}
	}

	return nil
}

type planShape struct {
	intervalS int
	count     int
	offsetS   int
}

// resetAll wipes the seed-managed rows in the unified races table
// (only finished | cancelled; live rows are removed via lobby
// cascade), plus the plan and queue tables. Drivers and clans are
// kept (they're independent of races).
func (r *Runner) resetAll(ctx context.Context) error {
	if _, err := r.pg.Exec(ctx, `DELETE FROM race_queue`); err != nil {
		return err
	}
	if _, err := r.pg.Exec(ctx, `DELETE FROM races`); err != nil {
		return err
	}
	if _, err := r.pg.Exec(ctx, `DELETE FROM race_plans`); err != nil {
		return err
	}
	if _, err := r.pg.Exec(ctx, `DELETE FROM track_calendar`); err != nil {
		return err
	}
	if _, err := r.pg.Exec(ctx, `DELETE FROM drivers`); err != nil {
		return err
	}
	if _, err := r.pg.Exec(ctx, `DELETE FROM clans`); err != nil {
		return err
	}
	if _, err := r.pg.Exec(ctx, `ALTER SEQUENCE IF EXISTS track_calendar_id_seq RESTART WITH 1`); err != nil {
		return err
	}
	for _, m := range r.lb.ListRaces() {
		_ = r.lb.DeleteRace(m.ID)
	}
	if _, err := r.pg.Exec(ctx, `DELETE FROM lobby_drivers`); err != nil {
		return err
	}
	return nil
}

// seedDriversAndClans inserts the default driver and clan set if the
// tables are empty. Idempotent: existing rows are left alone.
func (r *Runner) seedDriversAndClans(ctx context.Context) error {
	clanCount, err := r.clansPg.Count(ctx)
	if err != nil {
		return fmt.Errorf("count clans: %w", err)
	}
	if clanCount == 0 {
		now := time.Now().UnixMilli()
		for i, cs := range defaultClanSeeds {
			c := clans.Clan{
				ID:        fmt.Sprintf("clan-seed-%03d", i+1),
				Tag:       cs.tag,
				Name:      cs.name,
				AvatarURL: fmt.Sprintf("https://cdn.example.com/clans/%s.png", cs.tag),
				CreatedMs: now,
				UpdatedMs: now,
			}
			if err := r.clansPg.Create(ctx, c); err != nil {
				return fmt.Errorf("insert clan %s: %w", cs.tag, err)
			}
		}
	}
	drvCount, err := r.driversPg.Count(ctx)
	if err != nil {
		return fmt.Errorf("count drivers: %w", err)
	}
	if drvCount == 0 {
		now := time.Now().UnixMilli()
		// Round-robin: each driver assigned to one of the seeded clans.
		clanIDs := make([]string, 0, len(defaultClanSeeds))
		for i := range defaultClanSeeds {
			clanIDs = append(clanIDs, fmt.Sprintf("clan-seed-%03d", i+1))
		}
		for i, ds := range defaultDriverSeeds {
			d := drivers.Driver{
				ID:        fmt.Sprintf("driver-seed-%03d", i+1),
				Nickname:  ds.nick,
				Name:      ds.name,
				AvatarURL: fmt.Sprintf("https://cdn.example.com/drivers/%s.png", ds.nick),
				ClanID:    clanIDs[i%len(clanIDs)],
				CreatedMs: now,
				UpdatedMs: now,
			}
			if err := r.driversPg.Create(ctx, d); err != nil {
				return fmt.Errorf("insert driver %s: %w", ds.nick, err)
			}
		}
	}
	return nil
}

// loadTracks fills r.trackIDs from the tracks table. Falls back to
// fallbackTracks if the table is empty.
func (r *Runner) loadTracks(ctx context.Context) error {
	ids, err := r.pg.ListTrackIDs(ctx)
	if err != nil {
		return err
	}
	if len(ids) == 0 {
		ids = fallbackTracks
	}
	r.trackIDs = ids
	return nil
}

// loadDrivers fills r.driverIDs and r.driverInfo from the drivers table
// in the DB, then propagates the profile (nickname/avatar/clan) to the
// in-memory lobby drivers.
func (r *Runner) loadDrivers(ctx context.Context) error {
	// Pull all drivers, ordered by nickname.
	clanByID := make(map[string]string)
	clansList, err := r.clansPg.List(ctx, 200, 0)
	if err != nil {
		return fmt.Errorf("list clans: %w", err)
	}
	for _, c := range clansList {
		clanByID[c.ID] = c.Tag
	}
	r.clanByID = clanByID

	drvList, err := r.driversPg.List(ctx, 200, 0, "")
	if err != nil {
		return fmt.Errorf("list drivers: %w", err)
	}
	r.driverIDs = r.driverIDs[:0]
	r.driverInfo = r.driverInfo[:0]
	for _, d := range drvList {
		r.driverIDs = append(r.driverIDs, d.ID)
		r.driverInfo = append(r.driverInfo, seedDriver{
			ID:       d.ID,
			Nickname: d.Nickname,
			Name:     d.Name,
			ClanID:   d.ClanID,
			ClanTag:  clanByID[d.ClanID],
		})
	}
	return nil
}

// ---------------------------------------------------------------------------
// Generators
// ---------------------------------------------------------------------------

func (r *Runner) makeFinished(idx int) races.FinishedRace {
	rng := r.rng
	now := r.now
	// Spread across the last 30 days.
	back := time.Duration(30*24-rng.Intn(30*24-1)) * time.Hour
	finishedMs := now.Add(-back).UnixMilli()
	startedMs := finishedMs - randDuration(rng, 90, 600).Milliseconds()

	track := r.trackIDs[rng.Intn(len(r.trackIDs))]
	laps := trackLaps(track)

	// Pick 2..4 random drivers from the seeded set.
	shuffled := append([]seedDriver(nil), r.driverInfo...)
	rng.Shuffle(len(shuffled), func(i, j int) { shuffled[i], shuffled[j] = shuffled[j], shuffled[i] })
	n := 2 + rng.Intn(3) // 2..4 drivers
	if n > len(shuffled) {
		n = len(shuffled)
	}
	picked := shuffled[:n]
	driverIDs := make([]string, n)
	for i, d := range picked {
		driverIDs[i] = d.ID
	}

	winner := picked[rng.Intn(len(picked))]
	totalLaps := laps
	if rng.Intn(5) == 0 {
		// ~20% DNF/partial.
		totalLaps = rng.Intn(laps)
	}
	bestLapMs := int64(20_000 + rng.Intn(8_000))

	// Per-driver total time. The winner is fastest; the rest are
	// winner's time + 2..16 seconds. Build the Results slice with
	// computed positions.
	perDriver := make([]int64, len(picked))
	for i, d := range picked {
		if d.ID == winner.ID {
			perDriver[i] = int64(totalLaps) * bestLapMs
		} else {
			perDriver[i] = int64(totalLaps)*bestLapMs + int64(2+rng.Intn(15))*1000
		}
	}
	type dp struct {
		d    seedDriver
		time int64
	}
	all := make([]dp, len(picked))
	for i := range picked {
		all[i] = dp{picked[i], perDriver[i]}
	}
	// Insertion sort by time ascending.
	for i := 1; i < len(all); i++ {
		for j := i; j > 0 && all[j-1].time > all[j].time; j-- {
			all[j-1], all[j] = all[j], all[j-1]
		}
	}
	results := make([]races.DriverResult, 0, len(all))
	for i, row := range all {
		pos := i + 1
		// Podium only for the top-3; the rest are just DNF-ish finishers
		// (they have a time and a position).
		results = append(results, races.DriverResult{
			DriverID:    row.d.ID,
			TotalTimeMs: row.time,
			BestLapMs:   bestLapMs,
			Position:    &pos,
		})
	}

	return races.FinishedRace{
		ID:           fmt.Sprintf("seed-finished-%03d", idx+1),
		Name:         fmt.Sprintf("Seed Race #%d (%s)", idx+1, track),
		TrackID:      track,
		MaxCars:      4,
		Laps:         laps,
		TimeLimitS:   0,
		DriverIDs:    driverIDs,
		Status:       "finished",
		CreatedMs:    finishedMs - randDuration(rng, 5, 120).Milliseconds(),
		StartedMs:    startedMs,
		FinishedMs:   finishedMs,
		DurationMs:   finishedMs - startedMs,
		TotalLaps:    totalLaps,
		TotalDrivers: len(driverIDs),
		Results:      results,
	}
}

func (r *Runner) createLive(status lobby.RaceStatus, idx int) (lobby.RaceMeta, error) {
	rng := r.rng
	track := r.trackIDs[rng.Intn(len(r.trackIDs))]

	meta, err := r.lb.CreateRace(lobby.CreateRaceOptions{
		Name:       fmt.Sprintf("Live %s #%d", track, idx+1),
		TrackID:    track,
		MaxCars:    4,
		Laps:       trackLaps(track),
		TimeLimitS: 0,
	})
	if err != nil {
		return lobby.RaceMeta{}, err
	}
	// Add 1..3 random drivers into the race. We re-add them to refresh
	// any prior lobby state, then attach the profile (nickname/avatar/
	// clan) so the WS broadcast carries rich metadata.
	shuffled := append([]seedDriver(nil), r.driverInfo...)
	rng.Shuffle(len(shuffled), func(i, j int) { shuffled[i], shuffled[j] = shuffled[j], shuffled[i] })
	n := 1 + rng.Intn(3)
	if n > len(shuffled) {
		n = len(shuffled)
	}
	for i := 0; i < n; i++ {
		d := shuffled[i]
		r.lb.RemoveDriver(d.ID)
		if _, err := r.lb.AddDriver(d.ID, d.Name, ""); err != nil {
			continue
		}
		r.lb.SetDriverProfile(d.ID, d.Nickname, "", d.ClanID, d.ClanTag)
		devID := i
		_ = r.lb.SelectDevice(d.ID, &devID)
		if err := r.lb.AddDriverToRace(d.ID, meta.ID); err != nil {
			// ignore: race may be at capacity
		}
	}
	// Synchronously flush the race to the DB so the persistence mirror
	// (which uses detached goroutines) doesn't race with subsequent
	// status changes. The mirror calls in lobby.Service are still
	// fired; this upsert is a guarantee, not a replacement.
	if r.live != nil {
		flushCtx, flushCancel := context.WithTimeout(context.Background(), 2*time.Second)
		defer flushCancel()
		// Re-fetch the race from the in-memory lobby to get the latest
		// driver list and started_ms.
		cur, err := r.lb.GetRace(meta.ID)
		if err == nil {
			_ = r.live.UpsertRace(flushCtx, cur)
			for slot, did := range cur.DriverIDs {
				_ = r.live.AddDriver(flushCtx, cur.ID, did, slot)
			}
		}
	}
	_ = status
	return meta, nil
}

func (r *Runner) makePlan(idx int, ps planShape) races.RacePlan {
	rng := r.rng
	now := r.now
	track := r.trackIDs[rng.Intn(len(r.trackIDs))]
	startAt := now.Add(time.Duration(ps.offsetS) * time.Second).UnixMilli()
	return races.RacePlan{
		ID:         fmt.Sprintf("seed-plan-%03d", idx+1),
		Name:       fmt.Sprintf("Seed Plan #%d (%s)", idx+1, track),
		TrackID:    track,
		MaxCars:    4,
		Laps:       trackLaps(track),
		TimeLimitS: 0,
		StartAtMs:  startAt,
		IntervalS:  ps.intervalS,
		Count:      ps.count,
		Enabled:    true,
		NextFireMs: startAt,
	}
}

// ---------------------------------------------------------------------------
// helpers
// ---------------------------------------------------------------------------

func trackLaps(track string) int {
	switch track {
	case "nordschleife":
		return 3
	case "monza":
		return 12
	case "spa":
		return 10
	case "silverstone":
		return 8
	case "suzuka":
		return 9
	default:
		return 5
	}
}

func randDuration(rng *rand.Rand, loSec, hiSec int) time.Duration {
	return time.Duration(loSec+rng.Intn(hiSec-loSec+1)) * time.Second
}

func removeFrom(in []string, v string) []string {
	out := make([]string, 0, len(in)-1)
	for _, x := range in {
		if x != v {
			out = append(out, x)
		}
	}
	return out
}