package store

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

// HostRepoStats is the per-host projection of repo-level metrics.
// All pointer fields are nullable; nil means "not yet known." The row
// is created (or replaced) by UpsertHostRepoStats which merges in only
// the non-nil fields from a patch.
type HostRepoStats struct {
	HostID              string
	TotalSizeBytes      *int64
	RawSizeBytes        *int64
	UniqueFiles         *int64
	SnapshotCount       *int64
	LastCheckAt         *time.Time
	LastCheckStatus     string // "" | "ok" | "errors_found" | "failed"
	LockPresent         *bool
	LastPruneAt         *time.Time
	LastPruneFreedBytes *int64
	UpdatedAt           time.Time
}

// GetHostRepoStats returns the row, or (nil, ErrNotFound) if absent.
func (s *Store) GetHostRepoStats(ctx context.Context, hostID string) (*HostRepoStats, error) {
	row := s.db.QueryRowContext(ctx,
		`SELECT host_id, total_size_bytes, raw_size_bytes, unique_files,
		        snapshot_count, last_check_at, last_check_status,
		        lock_present, last_prune_at, last_prune_freed_bytes, updated_at
		 FROM host_repo_stats WHERE host_id = ?`, hostID)
	return scanHostRepoStats(row)
}

// getHostRepoStatsTx is identical to GetHostRepoStats but runs on an
// existing transaction so the fetch-merge-upsert in UpsertHostRepoStats
// is fully serialised.
func getHostRepoStatsTx(ctx context.Context, tx *sql.Tx, hostID string) (*HostRepoStats, error) {
	row := tx.QueryRowContext(ctx,
		`SELECT host_id, total_size_bytes, raw_size_bytes, unique_files,
		        snapshot_count, last_check_at, last_check_status,
		        lock_present, last_prune_at, last_prune_freed_bytes, updated_at
		 FROM host_repo_stats WHERE host_id = ?`, hostID)
	return scanHostRepoStats(row)
}

// scanHostRepoStats scans one row from host_repo_stats.
func scanHostRepoStats(row *sql.Row) (*HostRepoStats, error) {
	var (
		st              HostRepoStats
		totalSize       sql.NullInt64
		rawSize         sql.NullInt64
		uniqueFiles     sql.NullInt64
		snapshotCount   sql.NullInt64
		lastCheckAt     sql.NullString
		lastCheckStatus sql.NullString
		lockPresent     int64
		lastPruneAt     sql.NullString
		lastPruneFreed  sql.NullInt64
		updatedAt       string
	)
	if err := row.Scan(
		&st.HostID,
		&totalSize, &rawSize, &uniqueFiles, &snapshotCount,
		&lastCheckAt, &lastCheckStatus,
		&lockPresent,
		&lastPruneAt, &lastPruneFreed,
		&updatedAt,
	); err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return nil, ErrNotFound
		}
		return nil, fmt.Errorf("store: scan host_repo_stats: %w", err)
	}
	if totalSize.Valid {
		v := totalSize.Int64
		st.TotalSizeBytes = &v
	}
	if rawSize.Valid {
		v := rawSize.Int64
		st.RawSizeBytes = &v
	}
	if uniqueFiles.Valid {
		v := uniqueFiles.Int64
		st.UniqueFiles = &v
	}
	if snapshotCount.Valid {
		v := snapshotCount.Int64
		st.SnapshotCount = &v
	}
	if lastCheckAt.Valid {
		t, err := time.Parse(time.RFC3339Nano, lastCheckAt.String)
		if err != nil {
			return nil, fmt.Errorf("store: parse last_check_at: %w", err)
		}
		st.LastCheckAt = &t
	}
	if lastCheckStatus.Valid {
		st.LastCheckStatus = lastCheckStatus.String
	}
	lp := lockPresent != 0
	st.LockPresent = &lp
	if lastPruneAt.Valid {
		t, err := time.Parse(time.RFC3339Nano, lastPruneAt.String)
		if err != nil {
			return nil, fmt.Errorf("store: parse last_prune_at: %w", err)
		}
		st.LastPruneAt = &t
	}
	if lastPruneFreed.Valid {
		v := lastPruneFreed.Int64
		st.LastPruneFreedBytes = &v
	}
	t, err := time.Parse(time.RFC3339Nano, updatedAt)
	if err != nil {
		return nil, fmt.Errorf("store: parse host_repo_stats.updated_at: %w", err)
	}
	st.UpdatedAt = t
	return &st, nil
}

// UpsertHostRepoStats writes a partial update — only non-nil pointer
// fields (and LastCheckStatus when non-empty) overwrite existing
// columns. Wrapped in a transaction so concurrent upserts on the same
// host don't lose updates.
func (s *Store) UpsertHostRepoStats(ctx context.Context, hostID string, patch HostRepoStats) error {
	tx, err := s.db.BeginTx(ctx, nil)
	if err != nil {
		return fmt.Errorf("store: begin host_repo_stats tx: %w", err)
	}
	defer func() { _ = tx.Rollback() }()

	// Fetch existing row; start from zero if absent.
	cur, err := getHostRepoStatsTx(ctx, tx, hostID)
	if err != nil && !errors.Is(err, ErrNotFound) {
		return err
	}
	if cur == nil {
		cur = &HostRepoStats{HostID: hostID}
	}

	// Merge: non-nil patch fields overwrite current.
	if patch.TotalSizeBytes != nil {
		cur.TotalSizeBytes = patch.TotalSizeBytes
	}
	if patch.RawSizeBytes != nil {
		cur.RawSizeBytes = patch.RawSizeBytes
	}
	if patch.UniqueFiles != nil {
		cur.UniqueFiles = patch.UniqueFiles
	}
	if patch.SnapshotCount != nil {
		cur.SnapshotCount = patch.SnapshotCount
	}
	if patch.LastCheckAt != nil {
		cur.LastCheckAt = patch.LastCheckAt
	}
	if patch.LastCheckStatus != "" {
		cur.LastCheckStatus = patch.LastCheckStatus
	}
	if patch.LockPresent != nil {
		cur.LockPresent = patch.LockPresent
	}
	if patch.LastPruneAt != nil {
		cur.LastPruneAt = patch.LastPruneAt
	}
	if patch.LastPruneFreedBytes != nil {
		cur.LastPruneFreedBytes = patch.LastPruneFreedBytes
	}

	now := time.Now().UTC().Format(time.RFC3339Nano)

	// Convert *bool → int for lock_present.
	var lockPresentInt int64
	if cur.LockPresent != nil && *cur.LockPresent {
		lockPresentInt = 1
	}

	if _, err = tx.ExecContext(ctx,
		`INSERT INTO host_repo_stats
		   (host_id, total_size_bytes, raw_size_bytes, unique_files,
		    snapshot_count, last_check_at, last_check_status,
		    lock_present, last_prune_at, last_prune_freed_bytes, updated_at)
		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
		 ON CONFLICT(host_id) DO UPDATE SET
		   total_size_bytes       = excluded.total_size_bytes,
		   raw_size_bytes         = excluded.raw_size_bytes,
		   unique_files           = excluded.unique_files,
		   snapshot_count         = excluded.snapshot_count,
		   last_check_at          = excluded.last_check_at,
		   last_check_status      = excluded.last_check_status,
		   lock_present           = excluded.lock_present,
		   last_prune_at          = excluded.last_prune_at,
		   last_prune_freed_bytes = excluded.last_prune_freed_bytes,
		   updated_at             = excluded.updated_at`,
		hostID,
		nullableInt64(cur.TotalSizeBytes),
		nullableInt64(cur.RawSizeBytes),
		nullableInt64(cur.UniqueFiles),
		nullableInt64(cur.SnapshotCount),
		nullableTime(cur.LastCheckAt),
		nullableStr(cur.LastCheckStatus),
		lockPresentInt,
		nullableTime(cur.LastPruneAt),
		nullableInt64(cur.LastPruneFreedBytes),
		now,
	); err != nil {
		return fmt.Errorf("store: upsert host_repo_stats: %w", err)
	}

	// Project total_size_bytes onto the dashboard's host row so the
	// "Repo size" column and FleetSummary.SUM(repo_size_bytes) stay in
	// sync with the latest report. We only write a non-nil size — a
	// patch that doesn't carry a size (e.g. a prune-only ack) leaves
	// the prior row value alone.
	if cur.TotalSizeBytes != nil {
		if _, err = tx.ExecContext(ctx,
			`UPDATE hosts SET repo_size_bytes = ? WHERE id = ?`,
			*cur.TotalSizeBytes, hostID,
		); err != nil {
			return fmt.Errorf("store: project repo_size_bytes onto hosts row: %w", err)
		}
	}

	return tx.Commit()
}

// nullableInt64 converts *int64 to a database/sql-compatible nullable value.
func nullableInt64(p *int64) any {
	if p == nil {
		return nil
	}
	return *p
}

// nullableTime converts *time.Time to an RFC3339Nano string or nil.
func nullableTime(p *time.Time) any {
	if p == nil {
		return nil
	}
	return p.UTC().Format(time.RFC3339Nano)
}