kandev/apps/backend/internal/task/repository/sqlite/git_snapshots.go

// Package sqlite provides SQLite-based repository implementations.
package sqlite

import (
	"context"
	"encoding/json"
	"fmt"
	"time"

	"github.com/google/uuid"

	"github.com/kandev/kandev/internal/task/models"
)

// TriggeredByLiveMonitor identifies snapshots written by the orchestrator's live
// git status persistence path. Used to scope the upsert in
// UpsertLatestLiveGitSnapshot so we don't disturb archive/completion snapshots.
const TriggeredByLiveMonitor = "live_monitor"

// snapshotRankExpr is the ORDER BY ranking shared by GetLatestGitSnapshot and
// GetLatestGitSnapshotsBySessionIDs. Both selectors must pick the same row for
// a session, so the expression lives in one place:
//
//   - rank 0: an archive snapshot that is still authoritative — either its
//     owning task is still archived (terminal cumulative diff), or the task
//     was unarchived but not yet resumed and no non-archive snapshot newer
//     than this archive row exists yet (a reload in that window must not
//     regress to pre-archive state).
//   - rank 1: agent_completed snapshots from the current execution generation.
//   - rank 2: live_monitor snapshots (periodic polls; may race completion).
//   - rank 3: pre-archive completions and archive snapshots that are stale
//     (task unarchived AND a newer non-archive snapshot exists).
//
// Ties within a rank break by created_at DESC, then id DESC so the selection
// is deterministic even when Postgres stores multiple writes at the same
// microsecond timestamp.
const snapshotRankExpr = `
			CASE
				WHEN snapshot_type = 'archive' AND (
					EXISTS (
						SELECT 1 FROM task_sessions ts
						JOIN tasks t ON t.id = ts.task_id
						WHERE ts.id = task_session_git_snapshots.session_id
						  AND t.archived_at IS NOT NULL
					)
					OR NOT EXISTS (
						SELECT 1 FROM task_session_git_snapshots newer
						WHERE newer.session_id = task_session_git_snapshots.session_id
						  AND newer.snapshot_type <> 'archive'
						  AND newer.created_at > task_session_git_snapshots.created_at
					)
				) THEN 0
				WHEN triggered_by = 'agent_completed' AND EXISTS (
					SELECT 1 FROM task_session_git_snapshots archive
					WHERE archive.session_id = task_session_git_snapshots.session_id
					  AND archive.snapshot_type = 'archive'
					  AND archive.created_at > task_session_git_snapshots.created_at
				) THEN 3
				WHEN triggered_by = 'agent_completed' THEN 1
				WHEN snapshot_type = 'archive' THEN 3
				ELSE 2
			END,
			created_at DESC,
			id DESC`

// UpsertLatestLiveGitSnapshot keeps at most one cached "live monitor" snapshot
// per session by deleting any previous live row and inserting the new one in a
// single transaction. This is the cache that backs the sidebar diff badge for
// tasks whose executor isn't currently running.
func (r *Repository) UpsertLatestLiveGitSnapshot(ctx context.Context, snapshot *models.GitSnapshot) error {
	if snapshot == nil {
		return fmt.Errorf("snapshot is nil")
	}
	snapshot.SnapshotType = models.SnapshotTypeStatusUpdate
	snapshot.TriggeredBy = TriggeredByLiveMonitor
	if snapshot.ID == "" {
		snapshot.ID = uuid.New().String()
	}
	if snapshot.CreatedAt.IsZero() {
		snapshot.CreatedAt = time.Now().UTC()
	}

	tx, err := r.db.BeginTxx(ctx, nil)
	if err != nil {
		return fmt.Errorf("begin tx: %w", err)
	}
	defer func() { _ = tx.Rollback() }()

	if _, err := tx.ExecContext(ctx, r.db.Rebind(`
		DELETE FROM task_session_git_snapshots
		WHERE session_id = ? AND snapshot_type = ? AND triggered_by = ?
	`), snapshot.SessionID, string(models.SnapshotTypeStatusUpdate), TriggeredByLiveMonitor); err != nil {
		return fmt.Errorf("delete previous live snapshot: %w", err)
	}

	filesJSON, metadataJSON, err := serializeSnapshotJSON(snapshot)
	if err != nil {
		return err
	}

	if _, err := tx.ExecContext(ctx, r.db.Rebind(`
		INSERT INTO task_session_git_snapshots (
			id, session_id, snapshot_type, branch, remote_branch, head_commit, base_commit,
			ahead, behind, files, triggered_by, metadata, created_at
		) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
	`), snapshot.ID, snapshot.SessionID, string(snapshot.SnapshotType), snapshot.Branch,
		snapshot.RemoteBranch, snapshot.HeadCommit, snapshot.BaseCommit, snapshot.Ahead,
		snapshot.Behind, filesJSON, snapshot.TriggeredBy, metadataJSON, snapshot.CreatedAt); err != nil {
		return fmt.Errorf("insert live snapshot: %w", err)
	}

	return tx.Commit()
}

// serializeSnapshotJSON marshals a snapshot's Files and Metadata maps into
// their JSON-text column forms. Nil maps serialize to "{}" (the sentinel
// that scans back to a nil map), preserving the row shape for both SQLite
// and Postgres.
func serializeSnapshotJSON(snapshot *models.GitSnapshot) (string, string, error) {
	filesJSON := "{}"
	if snapshot.Files != nil {
		b, err := json.Marshal(snapshot.Files)
		if err != nil {
			return "", "", fmt.Errorf("failed to serialize git snapshot files: %w", err)
		}
		filesJSON = string(b)
	}
	metadataJSON := "{}"
	if snapshot.Metadata != nil {
		b, err := json.Marshal(snapshot.Metadata)
		if err != nil {
			return "", "", fmt.Errorf("failed to serialize git snapshot metadata: %w", err)
		}
		metadataJSON = string(b)
	}
	return filesJSON, metadataJSON, nil
}

// DeleteLiveMonitorSnapshots removes all live_monitor-triggered snapshots for a
// session. Called after creating an agent_completed snapshot to prevent stale
// live_monitor data from superseding the authoritative completion snapshot.
func (r *Repository) DeleteLiveMonitorSnapshots(ctx context.Context, sessionID string) error {
	_, err := r.db.ExecContext(ctx, r.db.Rebind(`
		DELETE FROM task_session_git_snapshots
		WHERE session_id = ? AND triggered_by = ?
	`), sessionID, TriggeredByLiveMonitor)
	return err
}

// CreateGitSnapshot inserts a new git snapshot into the database.
func (r *Repository) CreateGitSnapshot(ctx context.Context, snapshot *models.GitSnapshot) error {
	if snapshot.ID == "" {
		snapshot.ID = uuid.New().String()
	}
	if snapshot.CreatedAt.IsZero() {
		snapshot.CreatedAt = time.Now().UTC()
	}

	filesJSON, metadataJSON, err := serializeSnapshotJSON(snapshot)
	if err != nil {
		return err
	}

	_, err = r.db.ExecContext(ctx, r.db.Rebind(`
		INSERT INTO task_session_git_snapshots (
			id, session_id, snapshot_type, branch, remote_branch, head_commit, base_commit,
			ahead, behind, files, triggered_by, metadata, created_at
		) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
	`), snapshot.ID, snapshot.SessionID, string(snapshot.SnapshotType), snapshot.Branch,
		snapshot.RemoteBranch, snapshot.HeadCommit, snapshot.BaseCommit, snapshot.Ahead,
		snapshot.Behind, filesJSON, snapshot.TriggeredBy, metadataJSON, snapshot.CreatedAt)

	return err
}

func (r *Repository) getGitSnapshotByOrder(ctx context.Context, sessionID, orderDir string) (*models.GitSnapshot, error) {
	snapshot := &models.GitSnapshot{}
	var snapshotType string
	var filesJSON string
	var metadataJSON string

	query := fmt.Sprintf(`
		SELECT id, session_id, snapshot_type, branch, remote_branch, head_commit, base_commit,
		       ahead, behind, files, triggered_by, metadata, created_at
		FROM task_session_git_snapshots
		WHERE session_id = ?
		ORDER BY created_at %s LIMIT 1
	`, orderDir)
	err := r.ro.QueryRowContext(ctx, r.ro.Rebind(query), sessionID).Scan(
		&snapshot.ID, &snapshot.SessionID, &snapshotType, &snapshot.Branch,
		&snapshot.RemoteBranch, &snapshot.HeadCommit, &snapshot.BaseCommit,
		&snapshot.Ahead, &snapshot.Behind, &filesJSON, &snapshot.TriggeredBy,
		&metadataJSON, &snapshot.CreatedAt,
	)
	if err != nil {
		return nil, err
	}

	snapshot.SnapshotType = models.SnapshotType(snapshotType)
	if filesJSON != "" && filesJSON != "{}" {
		if err := json.Unmarshal([]byte(filesJSON), &snapshot.Files); err != nil {
			return nil, fmt.Errorf("failed to deserialize git snapshot files: %w", err)
		}
	}
	if metadataJSON != "" && metadataJSON != "{}" {
		if err := json.Unmarshal([]byte(metadataJSON), &snapshot.Metadata); err != nil {
			return nil, fmt.Errorf("failed to deserialize git snapshot metadata: %w", err)
		}
	}

	return snapshot, nil
}

// GetLatestGitSnapshot retrieves the best git snapshot for a session.
// An archive snapshot (terminal cumulative diff captured at archive time) is
// authoritative while its owning task is still archived, and also while the
// task is unarchived but not yet resumed (no newer non-archive snapshot
// exists yet); once a newer agent_completed / live_monitor row describes the
// current execution, it wins over the stale archive row.
// Returns sql.ErrNoRows if no snapshot is found.
func (r *Repository) GetLatestGitSnapshot(ctx context.Context, sessionID string) (*models.GitSnapshot, error) {
	query := `
		SELECT id, session_id, snapshot_type, branch, remote_branch, head_commit, base_commit,
		       ahead, behind, files, triggered_by, metadata, created_at
		FROM task_session_git_snapshots
		WHERE session_id = ?
		ORDER BY` + snapshotRankExpr + `
		LIMIT 1
	`
	return scanGitSnapshot(r.ro.QueryRowContext(ctx, r.ro.Rebind(query), sessionID))
}

// GetLatestGitSnapshotsBySessionIDs loads one authoritative snapshot per
// session in one query per placeholder-sized chunk. It mirrors
// GetLatestGitSnapshot's ranking (snapshotRankExpr) without introducing an
// N+1 read when task-list summaries repair historical rows.
func (r *Repository) GetLatestGitSnapshotsBySessionIDs(
	ctx context.Context,
	sessionIDs []string,
) (map[string]*models.GitSnapshot, error) {
	result := make(map[string]*models.GitSnapshot, len(sessionIDs))
	if len(sessionIDs) == 0 {
		return result, nil
	}
	for _, chunk := range chunkIDs(sessionIDs, sqliteMaxHostParams) {
		placeholders, args := buildInPlaceholders(chunk)
		query := `
			SELECT id, session_id, snapshot_type, branch, remote_branch, head_commit, base_commit,
			       ahead, behind, files, triggered_by, metadata, created_at
			FROM (
				SELECT id, session_id, snapshot_type, branch, remote_branch, head_commit, base_commit,
				       ahead, behind, files, triggered_by, metadata, created_at,
				       ROW_NUMBER() OVER (
					       PARTITION BY session_id
					       ORDER BY` + snapshotRankExpr + `
				       ) AS row_number
				FROM task_session_git_snapshots
				WHERE session_id IN (` + placeholders + `)
			) ranked
			WHERE row_number = 1
			ORDER BY session_id
		`
		rows, err := r.ro.QueryContext(ctx, r.ro.Rebind(query), args...)
		if err != nil {
			return nil, err
		}
		for rows.Next() {
			snapshot, scanErr := scanGitSnapshot(rows)
			if scanErr != nil {
				_ = rows.Close()
				return nil, scanErr
			}
			if _, exists := result[snapshot.SessionID]; !exists {
				result[snapshot.SessionID] = snapshot
			}
		}
		if err := rows.Err(); err != nil {
			_ = rows.Close()
			return nil, err
		}
		_ = rows.Close()
	}
	return result, nil
}

type gitSnapshotScanner interface {
	Scan(dest ...interface{}) error
}

// scanGitSnapshot scans one task_session_git_snapshots row (all 13 columns)
// into a GitSnapshot, decoding the JSON-text files/metadata columns. The "{}"
// sentinel scans back to nil maps so empty rows round-trip cleanly.
func scanGitSnapshot(scanner gitSnapshotScanner) (*models.GitSnapshot, error) {
	snapshot := &models.GitSnapshot{}
	var snapshotType string
	var filesJSON string
	var metadataJSON string
	if err := scanner.Scan(
		&snapshot.ID, &snapshot.SessionID, &snapshotType, &snapshot.Branch,
		&snapshot.RemoteBranch, &snapshot.HeadCommit, &snapshot.BaseCommit,
		&snapshot.Ahead, &snapshot.Behind, &filesJSON, &snapshot.TriggeredBy,
		&metadataJSON, &snapshot.CreatedAt,
	); err != nil {
		return nil, err
	}
	snapshot.SnapshotType = models.SnapshotType(snapshotType)
	if filesJSON != "" && filesJSON != "{}" {
		if err := json.Unmarshal([]byte(filesJSON), &snapshot.Files); err != nil {
			return nil, fmt.Errorf("failed to deserialize git snapshot files: %w", err)
		}
	}
	if metadataJSON != "" && metadataJSON != "{}" {
		if err := json.Unmarshal([]byte(metadataJSON), &snapshot.Metadata); err != nil {
			return nil, fmt.Errorf("failed to deserialize git snapshot metadata: %w", err)
		}
	}
	return snapshot, nil
}

// GetFirstGitSnapshot retrieves the oldest git snapshot for a session (first one created).
// Returns sql.ErrNoRows if no snapshot is found.
func (r *Repository) GetFirstGitSnapshot(ctx context.Context, sessionID string) (*models.GitSnapshot, error) {
	return r.getGitSnapshotByOrder(ctx, sessionID, "ASC")
}

// GetGitSnapshotsBySession retrieves all git snapshots for a session, ordered by created_at descending.
// If limit > 0, only that many snapshots are returned.
// Returns an empty slice if no snapshots are found.
func (r *Repository) GetGitSnapshotsBySession(ctx context.Context, sessionID string, limit int) ([]*models.GitSnapshot, error) {
	query := `
		SELECT id, session_id, snapshot_type, branch, remote_branch, head_commit, base_commit,
		       ahead, behind, files, triggered_by, metadata, created_at
		FROM task_session_git_snapshots
		WHERE session_id = ?
		ORDER BY created_at DESC
	`
	if limit > 0 {
		query += fmt.Sprintf(" LIMIT %d", limit)
	}

	rows, err := r.ro.QueryContext(ctx, r.ro.Rebind(query), sessionID)
	if err != nil {
		return nil, err
	}
	defer func() { _ = rows.Close() }()

	var result []*models.GitSnapshot
	for rows.Next() {
		snapshot := &models.GitSnapshot{}
		var snapshotType string
		var filesJSON string
		var metadataJSON string

		err := rows.Scan(
			&snapshot.ID, &snapshot.SessionID, &snapshotType, &snapshot.Branch,
			&snapshot.RemoteBranch, &snapshot.HeadCommit, &snapshot.BaseCommit,
			&snapshot.Ahead, &snapshot.Behind, &filesJSON, &snapshot.TriggeredBy,
			&metadataJSON, &snapshot.CreatedAt,
		)
		if err != nil {
			return nil, err
		}

		snapshot.SnapshotType = models.SnapshotType(snapshotType)
		if filesJSON != "" && filesJSON != "{}" {
			if err := json.Unmarshal([]byte(filesJSON), &snapshot.Files); err != nil {
				return nil, fmt.Errorf("failed to deserialize git snapshot files: %w", err)
			}
		}
		if metadataJSON != "" && metadataJSON != "{}" {
			if err := json.Unmarshal([]byte(metadataJSON), &snapshot.Metadata); err != nil {
				return nil, fmt.Errorf("failed to deserialize git snapshot metadata: %w", err)
			}
		}

		result = append(result, snapshot)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}

	return result, nil
}

// CreateSessionCommit inserts a new commit record into the database.
// Idempotent on (session_id, commit_sha): a commit already observed for this
// session is silently skipped rather than duplicated, since it can now be
// reported from more than one trigger (live commit events, the per-turn
// reconcile sweep, and archive capture) for the same underlying git commit.
// The returned bool reports whether a new row was actually inserted, so
// callers can distinguish a fresh observation from a re-observed duplicate
// for writer-health counters.
//
// pre_commit_snapshot_id / post_commit_snapshot_id are always written empty
// (commit.PreCommitSnapshotID / PostCommitSnapshotID are never populated by
// any caller). No writer for either column exists anywhere in this codebase;
// they do not link a commit row to the task_session_git_snapshots chain.
// Treat them as reserved/unpopulated, not as live data.
func (r *Repository) CreateSessionCommit(ctx context.Context, commit *models.SessionCommit) (bool, error) {
	if commit.ID == "" {
		commit.ID = uuid.New().String()
	}
	if commit.CreatedAt.IsZero() {
		commit.CreatedAt = time.Now().UTC()
	}

	result, err := r.db.ExecContext(ctx, r.db.Rebind(`
		INSERT INTO task_session_commits (
			id, session_id, commit_sha, parent_sha, author_name, author_email,
			commit_message, committed_at, pre_commit_snapshot_id, post_commit_snapshot_id,
			files_changed, insertions, deletions, created_at
		) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
		ON CONFLICT (session_id, commit_sha) DO NOTHING
	`), commit.ID, commit.SessionID, commit.CommitSHA, commit.ParentSHA,
		commit.AuthorName, commit.AuthorEmail, commit.CommitMessage, commit.CommittedAt,
		commit.PreCommitSnapshotID, commit.PostCommitSnapshotID, commit.FilesChanged,
		commit.Insertions, commit.Deletions, commit.CreatedAt)
	if err != nil {
		return false, err
	}

	// RowsAffected returns 0 on a conflict-skipped row in both SQLite and Postgres.
	rows, err := result.RowsAffected()
	if err != nil {
		return false, err
	}
	return rows > 0, nil
}

// GetSessionCommits retrieves all commits for a session, ordered by committed_at descending.
// Returns an empty slice if no commits are found.
func (r *Repository) GetSessionCommits(ctx context.Context, sessionID string) ([]*models.SessionCommit, error) {
	rows, err := r.ro.QueryContext(ctx, r.ro.Rebind(`
		SELECT id, session_id, commit_sha, parent_sha, author_name, author_email,
		       commit_message, committed_at, pre_commit_snapshot_id, post_commit_snapshot_id,
		       files_changed, insertions, deletions, created_at
		FROM task_session_commits
		WHERE session_id = ?
		ORDER BY committed_at DESC
	`), sessionID)
	if err != nil {
		return nil, err
	}
	defer func() { _ = rows.Close() }()

	var result []*models.SessionCommit
	for rows.Next() {
		commit := &models.SessionCommit{}
		err := rows.Scan(
			&commit.ID, &commit.SessionID, &commit.CommitSHA, &commit.ParentSHA,
			&commit.AuthorName, &commit.AuthorEmail, &commit.CommitMessage,
			&commit.CommittedAt, &commit.PreCommitSnapshotID, &commit.PostCommitSnapshotID,
			&commit.FilesChanged, &commit.Insertions, &commit.Deletions, &commit.CreatedAt,
		)
		if err != nil {
			return nil, err
		}
		result = append(result, commit)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}

	return result, nil
}

// GetLatestSessionCommit retrieves the most recent commit for a session.
// Returns sql.ErrNoRows if no commit is found.
func (r *Repository) GetLatestSessionCommit(ctx context.Context, sessionID string) (*models.SessionCommit, error) {
	commit := &models.SessionCommit{}

	err := r.ro.QueryRowContext(ctx, r.ro.Rebind(`
		SELECT id, session_id, commit_sha, parent_sha, author_name, author_email,
		       commit_message, committed_at, pre_commit_snapshot_id, post_commit_snapshot_id,
		       files_changed, insertions, deletions, created_at
		FROM task_session_commits
		WHERE session_id = ?
		ORDER BY committed_at DESC LIMIT 1
	`), sessionID).Scan(
		&commit.ID, &commit.SessionID, &commit.CommitSHA, &commit.ParentSHA,
		&commit.AuthorName, &commit.AuthorEmail, &commit.CommitMessage,
		&commit.CommittedAt, &commit.PreCommitSnapshotID, &commit.PostCommitSnapshotID,
		&commit.FilesChanged, &commit.Insertions, &commit.Deletions, &commit.CreatedAt,
	)
	if err != nil {
		return nil, err
	}

	return commit, nil
}

// DeleteSessionCommit removes a commit record from the database.
func (r *Repository) DeleteSessionCommit(ctx context.Context, id string) error {
	_, err := r.db.ExecContext(ctx, r.db.Rebind(`DELETE FROM task_session_commits WHERE id = ?`), id)
	return err
}