package store

import (
	"context"
	"database/sql"
	"errors"

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

// ReconcileClientSnapshot compares client evidence with this client's durable
// server rows. It intentionally performs no lifecycle mutation yet: callers
// receive only the safe local terminate/discard instructions.
func (store *Store) ReconcileClientSnapshot(ctx context.Context, clientID string, snapshot *rvboxv1.ReconcileSnapshot) (*rvboxv1.ReconcileResult, error) {
	if snapshot == nil {
		return nil, errors.New("missing client reconciliation snapshot")
	}
	result := &rvboxv1.ReconcileResult{}
	for _, client := range snapshot.GetRetainedCommands() {
		issue, err := domain.ParseUUIDv7(client.GetIssueUuid())
		if err != nil {
			return nil, err
		}
		input := domain.ReconcileInput{ClientEvidence: domain.ClientEvidenceRetained, ClientLifecycle: client.GetLifecycle(), ClientRevision: domain.CommandRevision(client.GetCommandRevision()), ClientLastEventSeq: client.GetLastClientEventSeq(), ImmutableHashMatches: true}
		if client.GetTombstoned() {
			input.ClientEvidence = domain.ClientEvidenceTombstone
		}
		var lifecycle uint32
		var revision, lastSequence uint64
		var hash []byte
		err = store.db.QueryRowContext(ctx, `SELECT lifecycle, revision, last_event_seq, immutable_request_sha256 FROM commands WHERE issue_uuid = ? AND client_id = ?`, issue[:], clientID).Scan(&lifecycle, &revision, &lastSequence, &hash)
		if err == nil {
			input.ServerPresent = true
			input.ServerLifecycle = rvboxv1.CommandLifecycle(lifecycle)
			input.ServerRevision = domain.CommandRevision(revision)
			input.ServerLastEventSeq = lastSequence
			input.ImmutableHashMatches = len(hash) == len(client.GetImmutableRequestSha256()) && string(hash) == string(client.GetImmutableRequestSha256())
		} else if !errors.Is(err, sql.ErrNoRows) {
			return nil, err
		} else {
			var tombstoneHash []byte
			err = store.db.QueryRowContext(ctx, `SELECT immutable_sha256 FROM command_tombstones WHERE issue_uuid = ? AND client_id = ?`, issue[:], clientID).Scan(&tombstoneHash)
			if err == nil {
				input.ServerHasTombstone = true
				input.ImmutableHashMatches = len(tombstoneHash) == len(client.GetImmutableRequestSha256()) && string(tombstoneHash) == string(client.GetImmutableRequestSha256())
			} else if !errors.Is(err, sql.ErrNoRows) {
				return nil, err
			}
		}
		decision, err := domain.DecideReconciliation(input)
		if err != nil && !errors.Is(err, domain.ErrReconcileContradiction) {
			return nil, err
		}
		switch decision.Action {
		case domain.ReconcileTerminateLocal:
			result.TerminateLocalIssueUuids = append(result.TerminateLocalIssueUuids, issue.String())
		case domain.ReconcileDiscardLocalTerminal:
			result.DiscardLocalTerminalIssueUuids = append(result.DiscardLocalTerminalIssueUuids, issue.String())
		}
	}
	return result, nil
}