package store

import (
	"context"
	"crypto/sha256"
	"database/sql"
	"encoding/binary"
	"errors"
	"time"

	rvboxv1 "github.com/rvbox/rvbox/gen/go/rvbox/v1"
	"github.com/rvbox/rvbox/internal/domain"
)

var ErrSignalDeliveryUnavailable = errors.New("signal delivery is unavailable for this command state")

type SignalInput struct {
	IssueUUID   domain.UUID
	ClientID    string
	RequestUUID domain.UUID
	Signal      rvboxv1.SignalKind
	Hash        [32]byte
	OccurredAt  time.Time
}

type SignalResult struct {
	CommandRevision uint64
	Duplicate       bool
	Cancelled       bool
	Pending         bool
}

type SignalIntent struct {
	IssueUUID       domain.UUID
	CommandRevision uint64
	Signal          rvboxv1.SignalKind
}

// SignalCommand cancels queued work locally or records a revision-bound,
// replayable signal intent for dispatched/accepted/running work. The session
// layer later exposes that intent and the client acknowledges it as a durable
// command event.
func (store *Store) SignalCommand(ctx context.Context, input SignalInput) (SignalResult, error) {
	if input.IssueUUID == (domain.UUID{}) || input.ClientID == "" || input.RequestUUID == (domain.UUID{}) || input.Signal < rvboxv1.SignalKind_SIGNAL_HUP || input.Signal > rvboxv1.SignalKind_SIGNAL_USR2 || input.Hash == [32]byte{} || input.OccurredAt.IsZero() {
		return SignalResult{}, errors.New("invalid signal request")
	}
	store.writeMu.Lock()
	defer store.writeMu.Unlock()
	database, err := store.openDatabase()
	if err != nil {
		return SignalResult{}, err
	}
	method := "signal_command"
	target := input.IssueUUID.String()
	if existing, found, lookupErr := lookupControlMutation(ctx, database, input.RequestUUID, method, target, input.Hash); lookupErr != nil {
		return SignalResult{}, lookupErr
	} else if found {
		if len(existing) != 8 {
			return SignalResult{}, ErrInvalidSegmentRecord
		}
		return SignalResult{CommandRevision: binary.BigEndian.Uint64(existing), Duplicate: true}, nil
	}
	tx, err := database.BeginTx(ctx, nil)
	if err != nil {
		return SignalResult{}, err
	}
	defer tx.Rollback()
	var lifecycle uint32
	var revision uint64
	var targetGeneration sql.NullInt64
	err = tx.QueryRowContext(ctx, `SELECT lifecycle, revision, target_session_generation FROM commands WHERE issue_uuid = ? AND client_id = ?`, input.IssueUUID[:], input.ClientID).Scan(&lifecycle, &revision, &targetGeneration)
	if errors.Is(err, sql.ErrNoRows) {
		return SignalResult{}, ErrCommandNotFound
	}
	if err != nil {
		return SignalResult{}, err
	}
	if lifecycle != uint32(rvboxv1.CommandLifecycle_COMMAND_QUEUED) && (lifecycle < uint32(rvboxv1.CommandLifecycle_COMMAND_DISPATCHED) || lifecycle > uint32(rvboxv1.CommandLifecycle_COMMAND_RUNNING) || !targetGeneration.Valid || targetGeneration.Int64 <= 0) {
		return SignalResult{}, ErrSignalDeliveryUnavailable
	}
	if lifecycle != uint32(rvboxv1.CommandLifecycle_COMMAND_QUEUED) {
		charge, chargeErr := EstimateCharge(ChargeInput{SQLiteRows: 1, IndexEntries: 1})
		if chargeErr != nil {
			return SignalResult{}, chargeErr
		}
		var commandCharged, closeout, clientCharged, serverCharged uint64
		if err := tx.QueryRowContext(ctx, `SELECT commands.charged_bytes, commands.closeout_remaining_bytes, clients.charged_bytes, storage_counters.command_charged_bytes
FROM commands JOIN clients ON clients.client_id = commands.client_id JOIN storage_counters ON storage_counters.singleton = 1
WHERE commands.issue_uuid = ? AND commands.client_id = ?`, input.IssueUUID[:], input.ClientID).Scan(&commandCharged, &closeout, &clientCharged, &serverCharged); err != nil {
			return SignalResult{}, err
		}
		freeBytes, freeErr := store.freeSpaceProbe.AvailableBytes(store.dataDir)
		if freeErr != nil {
			return SignalResult{}, freeErr
		}
		reservation, reserveErr := CheckReservation(store.quotaLimits, ReservationState{CommandTotalCharged: commandCharged, CloseoutRemaining: closeout, ClientTotalCharged: clientCharged, ServerTotalCharged: serverCharged, FilesystemFreeBytes: freeBytes}, ReservationRequest{ChargedBytes: charge})
		if reserveErr != nil {
			return SignalResult{}, reserveErr
		}
		if _, err := tx.ExecContext(ctx, `INSERT INTO signal_intents (request_uuid, issue_uuid, signal, command_revision, acknowledged, created_at) VALUES (?, ?, ?, ?, 0, ?)`, input.RequestUUID[:], input.IssueUUID[:], input.Signal, revision, input.OccurredAt.UTC().UnixNano()); err != nil {
			return SignalResult{}, err
		}
		if _, err := tx.ExecContext(ctx, `UPDATE commands SET charged_bytes = ?, closeout_remaining_bytes = ? WHERE issue_uuid = ? AND charged_bytes = ?`, reservation.CommandTotalCharged, reservation.CloseoutRemaining, input.IssueUUID[:], commandCharged); err != nil {
			return SignalResult{}, err
		}
		if _, err := tx.ExecContext(ctx, `UPDATE clients SET charged_bytes = ? WHERE client_id = ? AND charged_bytes = ?`, reservation.ClientTotalCharged, input.ClientID, clientCharged); err != nil {
			return SignalResult{}, err
		}
		if _, err := tx.ExecContext(ctx, `UPDATE storage_counters SET command_charged_bytes = ? WHERE singleton = 1 AND command_charged_bytes = ?`, reservation.ServerTotalCharged, serverCharged); err != nil {
			return SignalResult{}, err
		}
		result := make([]byte, 8)
		binary.BigEndian.PutUint64(result, revision)
		if _, err := tx.ExecContext(ctx, `INSERT INTO control_mutations (request_uuid, method, owner_kind, owner_id, target, immutable_sha256, assigned_revision, result, created_at) VALUES (?, ?, 'command', ?, ?, ?, ?, ?, ?)`, input.RequestUUID[:], method, input.IssueUUID.String(), target, input.Hash[:], revision, result, input.OccurredAt.UTC().UnixNano()); err != nil {
			return SignalResult{}, err
		}
		auditPayload := []byte{byte(input.Signal)}
		auditHash := sha256.Sum256(auditPayload)
		if _, err := tx.ExecContext(ctx, `INSERT INTO audit_events (occurred_at, source, action, outcome, compression, payload, raw_bytes, stored_bytes, sha256) VALUES (?, 'control', ?, 'success', 1, ?, ?, ?, ?)`, input.OccurredAt.UTC().UnixNano(), method, auditPayload, len(auditPayload), len(auditPayload), auditHash[:]); err != nil {
			return SignalResult{}, err
		}
		if err := tx.Commit(); err != nil {
			return SignalResult{}, err
		}
		return SignalResult{CommandRevision: revision, Pending: true}, nil
	}
	if revision == ^uint64(0) {
		return SignalResult{}, errors.New("command revision exhausted")
	}
	nextRevision := revision + 1
	if _, err := tx.ExecContext(ctx, `UPDATE commands SET lifecycle = ?, terminal_time = ?, revision = ? WHERE issue_uuid = ? AND client_id = ? AND lifecycle = ? AND revision = ?`, rvboxv1.CommandLifecycle_COMMAND_CANCELLED, input.OccurredAt.UTC().UnixNano(), nextRevision, input.IssueUUID[:], input.ClientID, rvboxv1.CommandLifecycle_COMMAND_QUEUED, revision); err != nil {
		return SignalResult{}, err
	}
	result := make([]byte, 8)
	binary.BigEndian.PutUint64(result, nextRevision)
	_, err = tx.ExecContext(ctx, `INSERT INTO control_mutations (request_uuid, method, owner_kind, owner_id, target, immutable_sha256, assigned_revision, result, created_at) VALUES (?, ?, 'command', ?, ?, ?, ?, ?, ?)`, input.RequestUUID[:], method, input.IssueUUID.String(), target, input.Hash[:], nextRevision, result, input.OccurredAt.UTC().UnixNano())
	if err != nil {
		return SignalResult{}, err
	}
	// Keep a compact audit digest; command text/stdin is never copied to the
	// audit payload.
	auditPayload := []byte{byte(input.Signal)}
	auditHash := sha256.Sum256(auditPayload)
	_, err = tx.ExecContext(ctx, `INSERT INTO audit_events (occurred_at, source, action, outcome, compression, payload, raw_bytes, stored_bytes, sha256) VALUES (?, 'control', ?, 'success', 1, ?, ?, ?, ?)`, input.OccurredAt.UTC().UnixNano(), method, auditPayload, len(auditPayload), len(auditPayload), auditHash[:])
	if err != nil {
		return SignalResult{}, err
	}
	if err := tx.Commit(); err != nil {
		return SignalResult{}, err
	}
	return SignalResult{CommandRevision: nextRevision, Cancelled: true}, nil
}

func (store *Store) PendingSignals(ctx context.Context, clientID string, generation uint64) ([]SignalIntent, error) {
	if clientID == "" || generation == 0 {
		return nil, errors.New("client ID and generation are required")
	}
	database, err := store.openDatabase()
	if err != nil {
		return nil, err
	}
	rows, err := database.QueryContext(ctx, `SELECT i.issue_uuid, i.command_revision, i.signal
FROM signal_intents i JOIN commands c ON c.issue_uuid = i.issue_uuid
WHERE c.client_id = ? AND c.target_session_generation = ? AND c.lifecycle BETWEEN 2 AND 4 AND i.acknowledged = 0
ORDER BY i.created_at, i.request_uuid`, clientID, generation)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var result []SignalIntent
	for rows.Next() {
		var encoded []byte
		var intent SignalIntent
		if err := rows.Scan(&encoded, &intent.CommandRevision, &intent.Signal); err != nil {
			return nil, err
		}
		if len(encoded) != len(domain.UUID{}) || intent.CommandRevision == 0 || intent.Signal < rvboxv1.SignalKind_SIGNAL_HUP || intent.Signal > rvboxv1.SignalKind_SIGNAL_USR2 {
			return nil, ErrInvalidSegmentRecord
		}
		copy(intent.IssueUUID[:], encoded)
		result = append(result, intent)
	}
	return result, rows.Err()
}