package main

import (
	"database/sql"
	"errors"
	"os"
	"path/filepath"
	"reflect"
	"testing"
)

type MockSqlDB struct {
	queries      []string
	mockedError  error
	mockedResult sql.Result
}

type MockResult struct {
	sql.Result
}

func (m *MockSqlDB) Execute(sql string) error {
	m.queries = append(m.queries, sql)

	if m.mockedError != nil {
		return m.mockedError
	}

	if m.mockedResult != nil {
		return nil
	}

	return nil
}

func TestGetMigrationsGathersSqlFiles(t *testing.T) {
	root := t.TempDir()
	os.WriteFile(filepath.Join(root, "0001.sql"), []byte("SELECT 1 from table;"), 0750)
	os.WriteFile(filepath.Join(root, "0002.sql"), []byte("--requires:0001.sql\nSELECT 1 from table;"), 0750)
	os.WriteFile(filepath.Join(root, "0003.sql"), []byte("--requires:0002.sql\nSELECT 1 from table;"), 0750)

	migrationGraph, err := NewMigrationGraphFromDirectory(root)
	migrations, _ := migrationGraph.GetLinearHistory()

	if len(migrations) != 3 {
		t.Errorf("Expected three migrations collected, got %d instead.", len(migrations))
	}

	if err != nil {
		t.Errorf("Expected no error returned, got %#v", err)
	}

	expected := []Migration{
		NewMigration(filepath.Join(root, "0001.sql"), "0001.sql", ""),
		NewMigration(filepath.Join(root, "0002.sql"), "0002.sql", "0001.sql"),
		NewMigration(filepath.Join(root, "0003.sql"), "0003.sql", "0002.sql"),
	}

	collected := []Migration{}

	for _, migration := range migrations {
		collected = append(collected, migration)
	}

	if !reflect.DeepEqual(collected, expected) {
		t.Errorf("Expected collected migrations to equal %#v, got %3v instead.", expected, collected)
	}
}

func TestGetMigrationsIgnoresNonMigrationFiles(t *testing.T) {
	root := t.TempDir()
	os.WriteFile(filepath.Join(root, "0001.sql"), []byte("SELECT 1 from table;"), 0750)
	os.WriteFile(filepath.Join(root, "0002.txt"), []byte("SELECT 1 from table;"), 0750)

	migrationGraph, err := NewMigrationGraphFromDirectory(root)
	migrations, _ := migrationGraph.GetLinearHistory()

	if len(migrations) != 1 {
		t.Errorf("Expected one migration collected, got %d instead.", len(migrations))
	}

	if err != nil {
		t.Errorf("Expected no error returned, got %#v", err)
	}
	expected := []Migration{
		NewMigration(filepath.Join(root, "0001.sql"), "0001.sql", ""),
	}
	collected := []Migration{}

	for _, migration := range migrations {
		collected = append(collected, migration)
	}

	if !reflect.DeepEqual(collected, expected) {
		t.Errorf("Expected collected migrations to equal %#v, got %#v instead.", expected, collected)
	}
}

func TestGetMigrationsReturnsErrorIfInvalidRootDirectory(t *testing.T) {
	migrationGraph, _ := NewMigrationGraphFromDirectory("not-root")
	migrations, err := migrationGraph.GetLinearHistory()

	if len(migrations) != 0 {
		t.Errorf("Did not expect any migrations returned, got %#v", migrations)
	}

	if err == nil {
		t.Errorf("Expected error, got nil.")
	}
}

func TestGetMigrationsParsesRequirementsInCommentHeaders(t *testing.T) {
	root := t.TempDir()
	os.WriteFile(filepath.Join(root, "0000.sql"), []byte("SELECT 1 from table;"), 0750)
	os.WriteFile(filepath.Join(root, "0001.sql"), []byte("-- requires: 0000.sql\nSELECT 1 from table;"), 0750)

	migrationGraph, _ := NewMigrationGraphFromDirectory(root)
	migrations, err := migrationGraph.GetLinearHistory()
	if err != nil {
		t.Errorf("Expected no error returned, got %#v", err)
	}

	collected := []Migration{}

	for _, migration := range migrations {
		collected = append(collected, migration)
	}
	expected := []Migration{
		NewMigration(filepath.Join(root, "0000.sql"), "0000.sql", ""),
		NewMigration(filepath.Join(root, "0001.sql"), "0001.sql", "0000.sql"),
	}

	if !reflect.DeepEqual(collected, expected) {
		t.Errorf("Expected collected migrations to equal %#v, got %#v instead.", expected, collected)
	}
}

func TestGetMigrationsIgnoresUnrecognizedCommentHeaders(t *testing.T) {
	root := t.TempDir()
	os.WriteFile(filepath.Join(root, "0001.sql"), []byte("-- randomheader\nSELECT 1 from table;"), 0750)

	migrationGraph, _ := NewMigrationGraphFromDirectory(root)
	migrations, err := migrationGraph.GetLinearHistory()
	if err != nil {
		t.Errorf("Expected no error returned, got %#v", err)
	}

	expected := []Migration{
		NewMigration(filepath.Join(root, "0001.sql"), "0001.sql", ""),
	}

	collected := []Migration{}

	for _, migration := range migrations {
		collected = append(collected, migration)
	}
	if !reflect.DeepEqual(collected, expected) {
		t.Errorf("Expected collected migrations to equal %#v, got %#v instead.", expected, collected)
	}
}

func TestMigrateRunsSqlOnDBConnection(t *testing.T) {
	mockDb := &MockSqlDB{}
	root := t.TempDir()
	migrationPath := filepath.Join(root, "0001.sql")
	migrationSql := "SELECT 1 FROM table;"
	os.WriteFile(migrationPath, []byte(migrationSql), 0750)

	migrationGraph, _ := NewMigrationGraphFromDirectory(root)
	migrations, err := migrationGraph.GetLinearHistory()
	err = migrations[0].Apply(mockDb)

	if err != nil {
		t.Errorf("Expected no error returned, got %#v", err)
	}

	if !reflect.DeepEqual(mockDb.queries, []string{migrationSql}) {
		t.Errorf("Expected queries %#v to be run, got %#v instead.", []string{migrationSql}, mockDb.queries)
	}
}

func TestMigrateReturnsErrorOnFailToReadMigrationFile(t *testing.T) {
	mockDb := &MockSqlDB{}
	root := t.TempDir()
	// Does not exist.
	migrationPath := filepath.Join(root, "0001.sql")

	migration := NewMigration(migrationPath, "0001.sql", "")
	err := migration.Apply(mockDb)

	if err == nil {
		t.Errorf("Expected error returned, got nil")
	}
}

func TestMigrateReturnsErrorOnFailToRunSQL(t *testing.T) {
	mockDb := &MockSqlDB{mockedError: errors.New("Test error!")}
	root := t.TempDir()
	migrationSql := "SELECT 1 FROM table;"

	migrationPath := filepath.Join(root, "0001.sql")
	os.WriteFile(migrationPath, []byte(migrationSql), 0750)
	migrationGraph, _ := NewMigrationGraphFromDirectory(root)
	migrations, err := migrationGraph.GetLinearHistory()

	err = migrations[0].Apply(mockDb)

	if err == nil {
		t.Errorf("Expected error returned, got nil")
	}
}