// Package engineversionstore implements the PostgreSQL-backed adapter
// for `ports.EngineVersionStore`.
//
// The package owns the on-disk shape of the `engine_versions` table
// defined in
// `galaxy/gamemaster/internal/adapters/postgres/migrations/00001_init.sql`
// and translates the schema-agnostic `ports.EngineVersionStore`
// interface declared in `internal/ports/engineversionstore.go` into
// concrete go-jet/v2 statements driven by the pgx driver.
//
// Insert maps PostgreSQL unique violations to engineversion.ErrConflict;
// Update applies a partial UPDATE driven by the non-nil pointer fields
// of UpdateEngineVersionInput; Deprecate is idempotent on the
// already-deprecated row; IsReferencedByActiveRuntime probes the
// runtime_records table for non-finished references.
package engineversionstore

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"strings"
	"time"

	"galaxy/gamemaster/internal/adapters/postgres/internal/sqlx"
	pgtable "galaxy/gamemaster/internal/adapters/postgres/jet/gamemaster/table"
	"galaxy/gamemaster/internal/domain/engineversion"
	"galaxy/gamemaster/internal/domain/runtime"
	"galaxy/gamemaster/internal/ports"

	pg "github.com/go-jet/jet/v2/postgres"
)

// emptyOptionsJSON is the default value persisted when a caller hands
// us an empty Options slice. It matches the SQL column default.
var emptyOptionsJSON = []byte("{}")

// Config configures one PostgreSQL-backed engine-version store. The
// store does not own the underlying *sql.DB lifecycle.
type Config struct {
	DB               *sql.DB
	OperationTimeout time.Duration
}

// Store persists Game Master engine-version registry rows in
// PostgreSQL.
type Store struct {
	db               *sql.DB
	operationTimeout time.Duration
}

// New constructs one PostgreSQL-backed engine-version store from cfg.
func New(cfg Config) (*Store, error) {
	if cfg.DB == nil {
		return nil, errors.New("new postgres engine version store: db must not be nil")
	}
	if cfg.OperationTimeout <= 0 {
		return nil, errors.New("new postgres engine version store: operation timeout must be positive")
	}
	return &Store{
		db:               cfg.DB,
		operationTimeout: cfg.OperationTimeout,
	}, nil
}

// engineVersionSelectColumns matches scanRow's column order.
var engineVersionSelectColumns = pg.ColumnList{
	pgtable.EngineVersions.Version,
	pgtable.EngineVersions.ImageRef,
	pgtable.EngineVersions.Options,
	pgtable.EngineVersions.Status,
	pgtable.EngineVersions.CreatedAt,
	pgtable.EngineVersions.UpdatedAt,
}

// Get returns the row identified by version. Returns
// engineversion.ErrNotFound when no row exists.
func (store *Store) Get(ctx context.Context, version string) (engineversion.EngineVersion, error) {
	if store == nil || store.db == nil {
		return engineversion.EngineVersion{}, errors.New("get engine version: nil store")
	}
	if strings.TrimSpace(version) == "" {
		return engineversion.EngineVersion{}, fmt.Errorf("get engine version: version must not be empty")
	}

	operationCtx, cancel, err := sqlx.WithTimeout(ctx, "get engine version", store.operationTimeout)
	if err != nil {
		return engineversion.EngineVersion{}, err
	}
	defer cancel()

	stmt := pg.SELECT(engineVersionSelectColumns).
		FROM(pgtable.EngineVersions).
		WHERE(pgtable.EngineVersions.Version.EQ(pg.String(version)))

	query, args := stmt.Sql()
	row := store.db.QueryRowContext(operationCtx, query, args...)
	got, err := scanRow(row)
	if sqlx.IsNoRows(err) {
		return engineversion.EngineVersion{}, engineversion.ErrNotFound
	}
	if err != nil {
		return engineversion.EngineVersion{}, fmt.Errorf("get engine version: %w", err)
	}
	return got, nil
}

// List returns every row whose status matches statusFilter (when
// non-nil), ordered by version ASC.
func (store *Store) List(ctx context.Context, statusFilter *engineversion.Status) ([]engineversion.EngineVersion, error) {
	if store == nil || store.db == nil {
		return nil, errors.New("list engine versions: nil store")
	}
	if statusFilter != nil && !statusFilter.IsKnown() {
		return nil, fmt.Errorf("list engine versions: status %q is unsupported", *statusFilter)
	}

	operationCtx, cancel, err := sqlx.WithTimeout(ctx, "list engine versions", store.operationTimeout)
	if err != nil {
		return nil, err
	}
	defer cancel()

	stmt := pg.SELECT(engineVersionSelectColumns).
		FROM(pgtable.EngineVersions)
	if statusFilter != nil {
		stmt = stmt.WHERE(pgtable.EngineVersions.Status.EQ(pg.String(string(*statusFilter))))
	}
	stmt = stmt.ORDER_BY(pgtable.EngineVersions.Version.ASC())

	query, args := stmt.Sql()
	rows, err := store.db.QueryContext(operationCtx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("list engine versions: %w", err)
	}
	defer rows.Close()

	versions := make([]engineversion.EngineVersion, 0)
	for rows.Next() {
		got, err := scanRow(rows)
		if err != nil {
			return nil, fmt.Errorf("list engine versions: scan: %w", err)
		}
		versions = append(versions, got)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("list engine versions: %w", err)
	}
	if len(versions) == 0 {
		return nil, nil
	}
	return versions, nil
}

// Insert installs record into the registry. Returns
// engineversion.ErrConflict when a row with the same version already
// exists.
func (store *Store) Insert(ctx context.Context, record engineversion.EngineVersion) error {
	if store == nil || store.db == nil {
		return errors.New("insert engine version: nil store")
	}
	if err := record.Validate(); err != nil {
		return fmt.Errorf("insert engine version: %w", err)
	}

	operationCtx, cancel, err := sqlx.WithTimeout(ctx, "insert engine version", store.operationTimeout)
	if err != nil {
		return err
	}
	defer cancel()

	options := record.Options
	if len(options) == 0 {
		options = emptyOptionsJSON
	}

	stmt := pgtable.EngineVersions.INSERT(
		pgtable.EngineVersions.Version,
		pgtable.EngineVersions.ImageRef,
		pgtable.EngineVersions.Options,
		pgtable.EngineVersions.Status,
		pgtable.EngineVersions.CreatedAt,
		pgtable.EngineVersions.UpdatedAt,
	).VALUES(
		record.Version,
		record.ImageRef,
		string(options),
		string(record.Status),
		record.CreatedAt.UTC(),
		record.UpdatedAt.UTC(),
	)

	query, args := stmt.Sql()
	if _, err := store.db.ExecContext(operationCtx, query, args...); err != nil {
		if sqlx.IsUniqueViolation(err) {
			return fmt.Errorf("insert engine version: %w", engineversion.ErrConflict)
		}
		return fmt.Errorf("insert engine version: %w", err)
	}
	return nil
}

// Update applies a partial update to one engine-version row.
// updated_at is always refreshed from input.Now. Returns
// engineversion.ErrNotFound when the row is absent.
func (store *Store) Update(ctx context.Context, input ports.UpdateEngineVersionInput) error {
	if store == nil || store.db == nil {
		return errors.New("update engine version: nil store")
	}
	if err := input.Validate(); err != nil {
		return err
	}

	operationCtx, cancel, err := sqlx.WithTimeout(ctx, "update engine version", store.operationTimeout)
	if err != nil {
		return err
	}
	defer cancel()

	now := input.Now.UTC()
	assignments := []any{
		pgtable.EngineVersions.UpdatedAt.SET(pg.TimestampzT(now)),
	}
	if input.ImageRef != nil {
		assignments = append(assignments,
			pgtable.EngineVersions.ImageRef.SET(pg.String(*input.ImageRef)))
	}
	if input.Options != nil {
		options := *input.Options
		if len(options) == 0 {
			options = emptyOptionsJSON
		}
		assignments = append(assignments,
			pgtable.EngineVersions.Options.SET(
				pg.StringExp(pg.CAST(pg.String(string(options))).AS("jsonb")),
			))
	}
	if input.Status != nil {
		assignments = append(assignments,
			pgtable.EngineVersions.Status.SET(pg.String(string(*input.Status))))
	}

	stmt := pgtable.EngineVersions.UPDATE(pgtable.EngineVersions.UpdatedAt).
		SET(assignments[0], assignments[1:]...).
		WHERE(pgtable.EngineVersions.Version.EQ(pg.String(input.Version)))

	query, args := stmt.Sql()
	result, err := store.db.ExecContext(operationCtx, query, args...)
	if err != nil {
		return fmt.Errorf("update engine version: %w", err)
	}
	affected, err := result.RowsAffected()
	if err != nil {
		return fmt.Errorf("update engine version: rows affected: %w", err)
	}
	if affected == 0 {
		return engineversion.ErrNotFound
	}
	return nil
}

// Deprecate sets `status=deprecated` and refreshes `updated_at` for
// version. Returns engineversion.ErrNotFound when no row exists.
// Calling Deprecate on an already deprecated row succeeds with no
// further mutation (idempotent).
func (store *Store) Deprecate(ctx context.Context, version string, now time.Time) error {
	if store == nil || store.db == nil {
		return errors.New("deprecate engine version: nil store")
	}
	if strings.TrimSpace(version) == "" {
		return fmt.Errorf("deprecate engine version: version must not be empty")
	}
	if now.IsZero() {
		return fmt.Errorf("deprecate engine version: now must not be zero")
	}

	operationCtx, cancel, err := sqlx.WithTimeout(ctx, "deprecate engine version", store.operationTimeout)
	if err != nil {
		return err
	}
	defer cancel()

	// Pre-check the row's existence so we can surface a precise
	// ErrNotFound; a 0-row affected from the UPDATE alone could mean
	// "missing" or "already deprecated".
	current, err := store.Get(operationCtx, version)
	if err != nil {
		return err
	}
	if current.Status == engineversion.StatusDeprecated {
		return nil
	}

	stmt := pgtable.EngineVersions.UPDATE(pgtable.EngineVersions.Status).
		SET(
			pgtable.EngineVersions.Status.SET(pg.String(string(engineversion.StatusDeprecated))),
			pgtable.EngineVersions.UpdatedAt.SET(pg.TimestampzT(now.UTC())),
		).
		WHERE(pgtable.EngineVersions.Version.EQ(pg.String(version)))

	query, args := stmt.Sql()
	if _, err := store.db.ExecContext(operationCtx, query, args...); err != nil {
		return fmt.Errorf("deprecate engine version: %w", err)
	}
	return nil
}

// Delete removes the row identified by version. Returns
// engineversion.ErrNotFound when no row matches. The adapter does not
// inspect runtime_records; the service layer guards against active
// references through IsReferencedByActiveRuntime before issuing Delete.
func (store *Store) Delete(ctx context.Context, version string) error {
	if store == nil || store.db == nil {
		return errors.New("delete engine version: nil store")
	}
	if strings.TrimSpace(version) == "" {
		return fmt.Errorf("delete engine version: version must not be empty")
	}

	operationCtx, cancel, err := sqlx.WithTimeout(ctx, "delete engine version", store.operationTimeout)
	if err != nil {
		return err
	}
	defer cancel()

	stmt := pgtable.EngineVersions.DELETE().
		WHERE(pgtable.EngineVersions.Version.EQ(pg.String(version)))

	query, args := stmt.Sql()
	result, err := store.db.ExecContext(operationCtx, query, args...)
	if err != nil {
		return fmt.Errorf("delete engine version: %w", err)
	}
	affected, err := result.RowsAffected()
	if err != nil {
		return fmt.Errorf("delete engine version: rows affected: %w", err)
	}
	if affected == 0 {
		return engineversion.ErrNotFound
	}
	return nil
}

// IsReferencedByActiveRuntime reports whether any non-finished and
// non-stopped runtime row currently references version through
// `current_engine_version`.
func (store *Store) IsReferencedByActiveRuntime(ctx context.Context, version string) (bool, error) {
	if store == nil || store.db == nil {
		return false, errors.New("is referenced by active runtime: nil store")
	}
	if strings.TrimSpace(version) == "" {
		return false, fmt.Errorf("is referenced by active runtime: version must not be empty")
	}

	operationCtx, cancel, err := sqlx.WithTimeout(ctx, "is referenced by active runtime", store.operationTimeout)
	if err != nil {
		return false, err
	}
	defer cancel()

	stmt := pg.SELECT(pg.Int32(1).AS("present")).
		FROM(pgtable.RuntimeRecords).
		WHERE(pg.AND(
			pgtable.RuntimeRecords.CurrentEngineVersion.EQ(pg.String(version)),
			pgtable.RuntimeRecords.Status.NOT_IN(
				pg.String(string(runtime.StatusFinished)),
				pg.String(string(runtime.StatusStopped)),
			),
		)).
		LIMIT(1)

	query, args := stmt.Sql()
	row := store.db.QueryRowContext(operationCtx, query, args...)
	var present int32
	if err := row.Scan(&present); err != nil {
		if sqlx.IsNoRows(err) {
			return false, nil
		}
		return false, fmt.Errorf("is referenced by active runtime: %w", err)
	}
	return true, nil
}

// rowScanner abstracts *sql.Row and *sql.Rows so scanRow can be shared
// across single-row and iterated reads.
type rowScanner interface {
	Scan(dest ...any) error
}

// scanRow scans one engine_versions row from rs.
func scanRow(rs rowScanner) (engineversion.EngineVersion, error) {
	var (
		version   string
		imageRef  string
		options   string
		status    string
		createdAt time.Time
		updatedAt time.Time
	)
	if err := rs.Scan(&version, &imageRef, &options, &status, &createdAt, &updatedAt); err != nil {
		return engineversion.EngineVersion{}, err
	}
	return engineversion.EngineVersion{
		Version:   version,
		ImageRef:  imageRef,
		Options:   []byte(options),
		Status:    engineversion.Status(status),
		CreatedAt: createdAt.UTC(),
		UpdatedAt: updatedAt.UTC(),
	}, nil
}

// Ensure Store satisfies the ports.EngineVersionStore interface at
// compile time.
var _ ports.EngineVersionStore = (*Store)(nil)