package inventory

import (
	"context"
	"errors"

	"github.com/jackc/pgx/v5"
)

// What a controller build knows of the store's schema (novox/hq issue 352): the highest migration it
// carries, recorded by its version when it serves, and the highest migration the store has applied. A
// put-back of the controller to a build that reaches less than the store is refused (gate.go), because
// such a controller starts behind its own records and judges with what it can read.

// RecordSchemaReach keeps the highest migration the build serving now carries.
func (i *Inventory) RecordSchemaReach(ctx context.Context, build string, reach int) error {
	if build == "" {
		return errors.New("a schema reach is recorded by a build's version, and this controller has none")
	}
	_, err := i.store.Pool().Exec(ctx,
		`insert into controller_schema (build, reach) values ($1, $2)
		 on conflict (build) do update set reach = excluded.reach, recorded = now()`, build, reach)
	return err
}

// SchemaReachOf is the highest migration a build carries, as it recorded when it served; false for a
// build that never did.
func (i *Inventory) SchemaReachOf(ctx context.Context, build string) (int, bool, error) {
	var reach int
	err := i.store.Pool().QueryRow(ctx, `select reach from controller_schema where build = $1`, build).Scan(&reach)
	if errors.Is(err, pgx.ErrNoRows) {
		return 0, false, nil
	}
	return reach, err == nil, err
}

// SchemaApplied is the highest migration the store has applied.
func (i *Inventory) SchemaApplied(ctx context.Context) (int, error) {
	var n *int
	if err := i.store.Pool().QueryRow(ctx, `select max(number) from migration`).Scan(&n); err != nil {
		return 0, err
	}
	if n == nil {
		return 0, nil
	}
	return *n, nil
}