feat: db migrations runner + 001_init.sql (full v3 schema, 5 cable_types seeded)

internal/db/migrate.go

@@ -0,0 +1,94 @@
+package db
+
+import (
+	"database/sql"
+	"embed"
+	"fmt"
+	"sort"
+	"strings"
+)
+
+//go:embed migrations/*.sql
+var migrationFS embed.FS
+
+// Migrate applies any pending SQL files from migrations/*.sql in
+// lexicographic order against the given *sql.DB. Applied filenames are
+// tracked in schema_migrations so each runs at most once. Idempotent.
+func Migrate(d *sql.DB) error {
+	if _, err := d.Exec(`
+		CREATE TABLE IF NOT EXISTS schema_migrations (
+			name        TEXT PRIMARY KEY,
+			applied_at  TEXT NOT NULL DEFAULT (datetime('now'))
+		)
+	`); err != nil {
+		return fmt.Errorf("create schema_migrations: %w", err)
+	}
+
+	applied, err := loadApplied(d)
+	if err != nil {
+		return err
+	}
+
+	entries, err := migrationFS.ReadDir("migrations")
+	if err != nil {
+		return fmt.Errorf("read migrations dir: %w", err)
+	}
+	names := make([]string, 0, len(entries))
+	for _, e := range entries {
+		if e.IsDir() || !strings.HasSuffix(e.Name(), ".sql") {
+			continue
+		}
+		names = append(names, e.Name())
+	}
+	sort.Strings(names)
+
+	for _, name := range names {
+		if applied[name] {
+			continue
+		}
+		body, err := migrationFS.ReadFile("migrations/" + name)
+		if err != nil {
+			return fmt.Errorf("read %s: %w", name, err)
+		}
+		if err := runMigration(d, name, string(body)); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func loadApplied(d *sql.DB) (map[string]bool, error) {
+	rows, err := d.Query("SELECT name FROM schema_migrations")
+	if err != nil {
+		return nil, fmt.Errorf("load applied: %w", err)
+	}
+	defer rows.Close()
+	out := map[string]bool{}
+	for rows.Next() {
+		var n string
+		if err := rows.Scan(&n); err != nil {
+			return nil, err
+		}
+		out[n] = true
+	}
+	return out, rows.Err()
+}
+
+func runMigration(d *sql.DB, name, body string) error {
+	tx, err := d.Begin()
+	if err != nil {
+		return fmt.Errorf("begin %s: %w", name, err)
+	}
+	if _, err := tx.Exec(body); err != nil {
+		_ = tx.Rollback()
+		return fmt.Errorf("apply %s: %w", name, err)
+	}
+	if _, err := tx.Exec("INSERT INTO schema_migrations (name) VALUES (?)", name); err != nil {
+		_ = tx.Rollback()
+		return fmt.Errorf("record %s: %w", name, err)
+	}
+	if err := tx.Commit(); err != nil {
+		return fmt.Errorf("commit %s: %w", name, err)
+	}
+	return nil
+}