package spool

import (
	"context"
	"fmt"

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

// ReconcileSnapshot is a consistent durable view. The caller sends it only
// after welcome and before admitting new dispatches on that session.
func (store *Store) ReconcileSnapshot(ctx context.Context) (*rvboxv1.ReconcileSnapshot, error) {
	result := &rvboxv1.ReconcileSnapshot{}
	rows, err := store.db.QueryContext(ctx, `SELECT issue_uuid, command_revision, phase, next_event_seq, immutable_sha256 FROM commands ORDER BY issue_uuid`)
	if err != nil {
		return nil, err
	}
	for rows.Next() {
		command, err := scanReconcileCommand(rows, false)
		if err != nil {
			_ = rows.Close()
			return nil, err
		}
		result.RetainedCommands = append(result.RetainedCommands, command)
	}
	if err := rows.Close(); err != nil {
		return nil, err
	}
	tombstones, err := store.db.QueryContext(ctx, `SELECT issue_uuid, command_revision, terminal_lifecycle, immutable_sha256 FROM command_tombstones ORDER BY acknowledged_at, issue_uuid`)
	if err != nil {
		return nil, err
	}
	defer tombstones.Close()
	for tombstones.Next() {
		var owner, digest []byte
		var revision uint64
		var lifecycle uint32
		if err := tombstones.Scan(&owner, &revision, &lifecycle, &digest); err != nil {
			return nil, err
		}
		if _, valid := copiedUUID(owner); !valid || len(digest) != 32 || revision == 0 || !isTerminalPhase(lifecycle) {
			return nil, ErrScriptState
		}
		result.RetainedCommands = append(result.RetainedCommands, &rvboxv1.ReconcileCommandState{IssueUuid: uuidText(owner), CommandRevision: revision, Lifecycle: rvboxv1.CommandLifecycle(lifecycle), Tombstoned: true, ImmutableRequestSha256: append([]byte(nil), digest...)})
	}
	if err := tombstones.Err(); err != nil {
		return nil, err
	}
	return result, nil
}

type reconcileRow interface {
	Scan(...any) error
}

func scanReconcileCommand(row reconcileRow, tombstoned bool) (*rvboxv1.ReconcileCommandState, error) {
	var owner, digest []byte
	var revision uint64
	var lifecycle uint32
	var nextSequence uint64
	if err := row.Scan(&owner, &revision, &lifecycle, &nextSequence, &digest); err != nil {
		return nil, err
	}
	if _, valid := copiedUUID(owner); !valid || len(digest) != 32 || revision == 0 || lifecycle == 0 || lifecycle > 11 || nextSequence == 0 {
		return nil, fmt.Errorf("%w: invalid reconciliation row", ErrScriptState)
	}
	return &rvboxv1.ReconcileCommandState{IssueUuid: uuidText(owner), CommandRevision: revision, Lifecycle: rvboxv1.CommandLifecycle(lifecycle), LastClientEventSeq: nextSequence - 1, Tombstoned: tombstoned, ImmutableRequestSha256: append([]byte(nil), digest...)}, nil
}

func uuidText(value []byte) string {
	parsed, _ := copiedUUID(value)
	return parsed.String()
}