package store

import (
	"bytes"
	"context"
	"crypto/sha256"
	"database/sql"
	"encoding/json"
	"fmt"
	"sort"
	"time"

	"github.com/cosmic-clash/cosmic-clash/server/domain"
)

const InitialConnectIdempotencyScope = "match.initial_connect"

const initialConnectMatchLockSQL = `SELECT playlist, state, revision
FROM matches WHERE match_id = $1 FOR UPDATE`

const initialConnectParticipantsSQL = `SELECT player_id, ticket_id, team, slot, connected_at,
    participation_active
FROM match_participants WHERE match_id = $1 ORDER BY player_id FOR UPDATE`

const initialConnectIdempotencyInsertSQL = `INSERT INTO idempotency_keys
    (scope, idempotency_key, payload_digest, result)
VALUES ($1, $2, $3, '{}'::jsonb) ON CONFLICT (scope, idempotency_key) DO NOTHING`

const initialConnectIdempotencySelectSQL = `SELECT payload_digest, result
FROM idempotency_keys WHERE scope = $1 AND idempotency_key = $2 FOR UPDATE`

const initialConnectMatchUpdateSQL = `UPDATE matches
SET state = $2, revision = revision + 1 WHERE match_id = $1
RETURNING revision`

const initialConnectDeactivateSQL = `UPDATE match_participants
SET participation_active = FALSE, abandoned_at = $3
WHERE match_id = $1 AND player_id = ANY($2)`

const initialConnectReleaseAllSQL = `UPDATE match_participants
SET participation_active = FALSE
WHERE match_id = $1 AND participation_active`

const initialConnectTicketNoShowSQL = `UPDATE queue_tickets q
SET state = 'FAILED', revision = revision + 1
FROM match_participants mp
WHERE mp.match_id = $1 AND mp.player_id = ANY($2)
  AND q.ticket_id = mp.ticket_id AND q.player_id = mp.player_id
  AND q.state IN ('ASSIGNMENT_READY', 'ASSIGNED', 'CONNECTING')`

const initialConnectTicketInnocentCancelSQL = `UPDATE queue_tickets q
SET state = 'QUEUED', expires_at = $2, revision = revision + 1
FROM match_participants mp
WHERE mp.match_id = $1 AND mp.player_id = ANY($3)
  AND q.ticket_id = mp.ticket_id AND q.player_id = mp.player_id
  AND q.state IN ('ASSIGNMENT_READY', 'ASSIGNED', 'CONNECTING')`

const initialConnectTicketConnectedLiveSQL = `UPDATE queue_tickets q
SET state = 'LIVE', revision = revision + 1
FROM match_participants mp
WHERE mp.match_id = $1 AND mp.player_id = ANY($2)
  AND q.ticket_id = mp.ticket_id AND q.player_id = mp.player_id
  AND q.state IN ('ASSIGNMENT_READY', 'ASSIGNED', 'CONNECTING')`

const initialConnectPenaltySQL = `INSERT INTO penalties
    (penalty_id, player_id, match_id, playlist, kind, starts_at, ends_at)
VALUES ($1, $2, $3, $4, 'INITIAL_CONNECT_NO_SHOW', $5, $6)
ON CONFLICT (penalty_id) DO NOTHING`

const initialConnectOutboxSQL = `INSERT INTO outbox
    (event_id, aggregate_type, aggregate_id, revision, event_type, payload)
VALUES ($1, 'match', $2, $3, 'state_changed', $4)
ON CONFLICT DO NOTHING`

type initialConnectParticipant struct {
	PlayerID    string
	TicketID    string
	Team        int
	Slot        int
	ConnectedAt sql.NullTime
	Active      bool
}

// ApplyInitialConnectPlan atomically reconciles the pre-live connect window.
// It is deliberately a store operation: no-show penalties and innocent-ticket
// requeue must commit with the match transition or neither may commit.
func ApplyInitialConnectPlan(ctx context.Context, db *sql.DB, matchID, idempotencyKey string, plan domain.InitialConnectPlan, now time.Time) error {
	validActionState := (plan.Action == domain.InitialConnectStart || plan.Action == domain.InitialConnectStartWithBot) && plan.MatchState == domain.Live || plan.Action == domain.InitialConnectCancel && plan.MatchState == domain.Cancelled
	if db == nil || matchID == "" || len(idempotencyKey) < 16 || len(idempotencyKey) > 128 || now.IsZero() || !validActionState {
		return fmt.Errorf("invalid initial-connect transaction arguments")
	}
	digest, err := initialConnectDigest(matchID, plan)
	if err != nil {
		return err
	}
	return RunSerializable(ctx, db, DefaultSerializableAttempts, func(ctx context.Context, tx *sql.Tx) error {
		inserted, err := tx.ExecContext(ctx, initialConnectIdempotencyInsertSQL, InitialConnectIdempotencyScope, idempotencyKey, digest[:])
		if err != nil {
			return err
		}
		count, err := inserted.RowsAffected()
		if err != nil {
			return err
		}
		if count == 0 {
			var prior []byte
			var result []byte
			if err := tx.QueryRowContext(ctx, initialConnectIdempotencySelectSQL, InitialConnectIdempotencyScope, idempotencyKey).Scan(&prior, &result); err != nil {
				return err
			}
			if !bytes.Equal(prior, digest[:]) {
				return fmt.Errorf("%w: conflicting initial-connect request", domain.ErrConflict)
			}
			return nil
		}
		var playlist, state string
		var revision int64
		if err := tx.QueryRowContext(ctx, initialConnectMatchLockSQL, matchID).Scan(&playlist, &state, &revision); err != nil {
			return err
		}
		if state != string(domain.AssignmentReady) && state != string(domain.Assigned) && state != string(domain.Connecting) {
			return fmt.Errorf("%w: match is not awaiting initial connect: %s", domain.ErrConflict, state)
		}
		participants, err := loadInitialConnectParticipants(ctx, tx, matchID)
		if err != nil {
			return err
		}
		if err := validateInitialConnectPlan(plan, participants, domain.Playlist(playlist)); err != nil {
			return fmt.Errorf("%w: %v", domain.ErrConflict, err)
		}
		if plan.Action == domain.InitialConnectCancel {
			if _, err := tx.ExecContext(ctx, initialConnectReleaseAllSQL, matchID); err != nil {
				return err
			}
		}
		if _, err := tx.ExecContext(ctx, initialConnectDeactivateSQL, matchID, initialConnectNoShowIDs(plan), now); err != nil {
			return err
		}
		if _, err := tx.ExecContext(ctx, initialConnectTicketNoShowSQL, matchID, initialConnectNoShowIDs(plan)); err != nil {
			return err
		}
		if plan.Action == domain.InitialConnectCancel {
			if _, err := tx.ExecContext(ctx, initialConnectTicketInnocentCancelSQL, matchID, now.Add(domain.QueueExpiryWindow), plan.Connected); err != nil {
				return err
			}
		} else if _, err := tx.ExecContext(ctx, initialConnectTicketConnectedLiveSQL, matchID, plan.Connected); err != nil {
			return err
		}
		for _, noShow := range plan.NoShows {
			penaltyID := "initial-connect:" + matchID + ":" + noShow.PlayerID
			if _, err := tx.ExecContext(ctx, initialConnectPenaltySQL, penaltyID, noShow.PlayerID, matchID, playlist, noShow.AbandonedAt, noShow.AbandonedAt.Add(noShow.Cooldown)); err != nil {
				return err
			}
		}
		var finalRevision int64
		if err := tx.QueryRowContext(ctx, initialConnectMatchUpdateSQL, matchID, string(plan.MatchState)).Scan(&finalRevision); err != nil {
			return err
		}
		payload, _ := json.Marshal(map[string]any{"match_id": matchID, "state": plan.MatchState, "action": plan.Action})
		if _, err := tx.ExecContext(ctx, initialConnectOutboxSQL, "initial-connect:"+matchID+fmt.Sprintf(":%d", finalRevision), matchID, finalRevision, payload); err != nil {
			return err
		}
		stored, _ := json.Marshal(map[string]any{"match_id": matchID, "state": plan.MatchState, "revision": finalRevision})
		_, err = tx.ExecContext(ctx, `UPDATE idempotency_keys SET result = $3 WHERE scope = $1 AND idempotency_key = $2`, InitialConnectIdempotencyScope, idempotencyKey, stored)
		return err
	})
}

func initialConnectNoShowIDs(plan domain.InitialConnectPlan) []string {
	result := make([]string, len(plan.NoShows))
	for i := range plan.NoShows {
		result[i] = plan.NoShows[i].PlayerID
	}
	return result
}

func initialConnectDigest(matchID string, plan domain.InitialConnectPlan) ([32]byte, error) {
	copyPlan := plan
	sort.Strings(copyPlan.Connected)
	sort.Slice(copyPlan.NoShows, func(i, j int) bool { return copyPlan.NoShows[i].PlayerID < copyPlan.NoShows[j].PlayerID })
	b, err := json.Marshal(struct {
		MatchID string
		Plan    domain.InitialConnectPlan
	}{matchID, copyPlan})
	if err != nil {
		return [32]byte{}, err
	}
	return sha256.Sum256(b), nil
}

func loadInitialConnectParticipants(ctx context.Context, tx *sql.Tx, matchID string) ([]initialConnectParticipant, error) {
	rows, err := tx.QueryContext(ctx, initialConnectParticipantsSQL, matchID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var result []initialConnectParticipant
	for rows.Next() {
		var p initialConnectParticipant
		if err := rows.Scan(&p.PlayerID, &p.TicketID, &p.Team, &p.Slot, &p.ConnectedAt, &p.Active); err != nil {
			return nil, err
		}
		result = append(result, p)
	}
	return result, rows.Err()
}

func validateInitialConnectPlan(plan domain.InitialConnectPlan, participants []initialConnectParticipant, playlist domain.Playlist) error {
	if len(participants) == 0 || (plan.Action == domain.InitialConnectStartWithBot && playlist != domain.Casual) || (plan.Action == domain.InitialConnectCancel && plan.MatchState != domain.Cancelled) || (plan.Action == domain.InitialConnectStart && (plan.MatchState != domain.Live || len(plan.NoShows) != 0 || len(plan.CasualLineup) != 0)) {
		return fmt.Errorf("invalid initial-connect plan")
	}
	known, connected, missing := map[string]bool{}, map[string]bool{}, map[string]bool{}
	stored := make(map[string]initialConnectParticipant, len(participants))
	for _, p := range participants {
		if p.PlayerID == "" || !p.Active || p.Team < 0 || p.Team > 1 || p.Slot < 0 || p.Slot > 5 || p.Slot/3 != p.Team || known[p.PlayerID] {
			return fmt.Errorf("invalid stored participant roster")
		}
		known[p.PlayerID] = true
		stored[p.PlayerID] = p
		if p.ConnectedAt.Valid {
			connected[p.PlayerID] = true
		}
	}
	for _, id := range plan.Connected {
		if !known[id] || !connected[id] || missing[id] {
			return fmt.Errorf("invalid connected participant")
		}
		missing[id] = true
	}
	for _, noShow := range plan.NoShows {
		if !known[noShow.PlayerID] || connected[noShow.PlayerID] || missing[noShow.PlayerID] || noShow.Cooldown <= 0 || noShow.AbandonedAt.IsZero() {
			return fmt.Errorf("invalid no-show participant")
		}
		missing[noShow.PlayerID] = true
	}
	if len(missing) != len(known) {
		return fmt.Errorf("initial-connect plan does not cover roster")
	}
	if plan.Action == domain.InitialConnectStart && len(connected) != len(known) {
		return fmt.Errorf("initial-connect start requires complete connected roster")
	}
	if plan.Action == domain.InitialConnectStartWithBot {
		if len(plan.CasualLineup) != 6 {
			return fmt.Errorf("casual bot lineup must contain six players")
		}
		lineupSlots := make(map[int]bool, 6)
		lineupPlayers := make(map[string]bool, 6)
		for _, slot := range plan.CasualLineup {
			if slot.Slot < 0 || slot.Slot > 5 || slot.Team != slot.Slot/3 || lineupSlots[slot.Slot] || slot.PlayerID == "" || lineupPlayers[slot.PlayerID] {
				return fmt.Errorf("invalid casual bot lineup")
			}
			lineupSlots[slot.Slot] = true
			lineupPlayers[slot.PlayerID] = true
			if slot.IsBot {
				continue
			}
			if !connected[slot.PlayerID] {
				return fmt.Errorf("lineup contains non-connected human")
			}
			participant := stored[slot.PlayerID]
			if participant.Slot != slot.Slot || participant.Team != slot.Team {
				return fmt.Errorf("lineup moves connected human from assigned slot")
			}
		}
		for id := range connected {
			if !lineupPlayers[id] {
				return fmt.Errorf("lineup omits connected human")
			}
		}
	}
	return nil
}