package core

import (
	"context"
	"database/sql"
	"io"
	"io/fs"
	"log/slog"
	"path/filepath"
	"strings"
	"testing"

	"github.com/mithral/vellum/migrations"
)

func discardLogger() *slog.Logger {
	return slog.New(slog.NewTextHandler(io.Discard, nil))
}

// highestMigrationNumber reads the embedded migrations so the version
// assertion does not need editing every time a migration is added.
func highestMigrationNumber(t *testing.T) int {
	t.Helper()
	names, err := fs.Glob(migrations.FS, "*.sql")
	if err != nil {
		t.Fatal(err)
	}
	highest := 0
	for _, name := range names {
		n, err := migrationNumber(name)
		if err != nil {
			t.Fatal(err)
		}
		if n > highest {
			highest = n
		}
	}
	return highest
}

func openTempDB(t *testing.T) *sql.DB {
	t.Helper()
	db, err := OpenDB(filepath.Join(t.TempDir(), "test.db"))
	if err != nil {
		t.Fatalf("OpenDB: %v", err)
	}
	t.Cleanup(func() { _ = db.Close() })
	return db
}

func TestMigrateAppliesAndIsIdempotent(t *testing.T) {
	ctx := context.Background()
	db := openTempDB(t)

	if err := Migrate(ctx, db, migrations.FS, discardLogger()); err != nil {
		t.Fatalf("first Migrate: %v", err)
	}

	// Running again must be a no-op, not an error.
	if err := Migrate(ctx, db, migrations.FS, discardLogger()); err != nil {
		t.Fatalf("second Migrate (should be no-op): %v", err)
	}

	var version int
	if err := db.QueryRowContext(ctx, "PRAGMA user_version").Scan(&version); err != nil {
		t.Fatalf("read user_version: %v", err)
	}
	want := highestMigrationNumber(t)
	if version != want {
		t.Errorf("user_version = %d, want %d", version, want)
	}

	var tables int
	if err := db.QueryRowContext(ctx,
		"SELECT count(*) FROM sqlite_master WHERE type='table'").Scan(&tables); err != nil {
		t.Fatalf("count tables: %v", err)
	}
	if tables < 16 {
		t.Errorf("table count = %d, want >= 16", tables)
	}

	// WAL must be active: progress writes during a scan depend on it.
	var mode string
	if err := db.QueryRowContext(ctx, "PRAGMA journal_mode").Scan(&mode); err != nil {
		t.Fatalf("read journal_mode: %v", err)
	}
	if !strings.EqualFold(mode, "wal") {
		t.Errorf("journal_mode = %q, want wal", mode)
	}
}

func TestForeignKeyEnforcementIsOn(t *testing.T) {
	ctx := context.Background()
	db := openTempDB(t)
	if err := Migrate(ctx, db, migrations.FS, discardLogger()); err != nil {
		t.Fatalf("Migrate: %v", err)
	}

	// library_grants references users and libraries; neither 999 exists.
	_, err := db.ExecContext(ctx,
		"INSERT INTO library_grants(user_id, library_id) VALUES (999, 999)")
	if err == nil {
		t.Fatal("expected foreign key violation, got nil")
	}
}

func TestMigrationNumber(t *testing.T) {
	cases := map[string]int{
		"0001_core.sql":       1,
		"0042_audiobooks.sql": 42,
		"7_shorthand.sql":     7,
		"0010_no_ext":         10,
	}
	for name, want := range cases {
		got, err := migrationNumber(name)
		if err != nil {
			t.Errorf("migrationNumber(%q): %v", name, err)
			continue
		}
		if got != want {
			t.Errorf("migrationNumber(%q) = %d, want %d", name, got, want)
		}
	}

	if _, err := migrationNumber("core.sql"); err == nil {
		t.Error("expected error for filename without a numeric prefix")
	}
}

func TestSplitStatementsIgnoresComments(t *testing.T) {
	in := `
-- a comment with a semicolon; which must not split
CREATE TABLE a (id INTEGER); -- trailing comment;
/* block; comment; here */
CREATE TABLE b (id INTEGER);
`
	got := splitStatements(in)
	if len(got) != 2 {
		t.Fatalf("got %d statements, want 2: %#v", len(got), got)
	}
	if !strings.Contains(got[0], "CREATE TABLE a") {
		t.Errorf("statement 0 = %q", got[0])
	}
	if !strings.Contains(got[1], "CREATE TABLE b") {
		t.Errorf("statement 1 = %q", got[1])
	}
}

func TestSplitStatementsKeepsTriggerBodiesWhole(t *testing.T) {
	in := `
CREATE TABLE t (id INTEGER, name TEXT);
CREATE TRIGGER t_ai AFTER INSERT ON t BEGIN
  INSERT INTO t(name) VALUES (new.name);
  UPDATE t SET name = 'x' WHERE id = new.id;
END;
CREATE TABLE after_trigger (id INTEGER);
`
	got := splitStatements(in)
	if len(got) != 3 {
		t.Fatalf("got %d statements, want 3:\n%#v", len(got), got)
	}
	if !strings.Contains(got[1], "CREATE TRIGGER") || !strings.Contains(got[1], "END") {
		t.Errorf("trigger was split apart: %q", got[1])
	}
	if n := strings.Count(got[1], ";"); n != 2 {
		t.Errorf("trigger body has %d semicolons, want 2 (the internal ones)", n)
	}
	if !strings.Contains(got[2], "after_trigger") {
		t.Errorf("statement after the trigger = %q", got[2])
	}
}