package postgres

import (
	"context"
	"database/sql"
	"database/sql/driver"
	"errors"
	"io"
	"net/url"
	"strings"
	"sync"
	"testing"
)

func withPostgresPackageTestState(t *testing.T) {
	t.Helper()

	oldSQLOpen := sqlOpen
	oldPingDB := pingDB
	t.Cleanup(func() {
		sqlOpen = oldSQLOpen
		pingDB = oldPingDB
	})
}

func TestBuildDSNInjectsCredentials(t *testing.T) {
	dsn, err := BuildDSN(ConnConfig{
		URI:      " postgres://db.example.local:5432/feedkit?sslmode=disable ",
		Username: "app_user",
		Password: "app_pass",
	})
	if err != nil {
		t.Fatalf("BuildDSN() error = %v", err)
	}

	u, err := url.Parse(dsn)
	if err != nil {
		t.Fatalf("url.Parse() error = %v", err)
	}
	if u.User == nil || u.User.Username() != "app_user" {
		t.Fatalf("username = %q, want app_user", u.User.Username())
	}
	pass, ok := u.User.Password()
	if !ok || pass != "app_pass" {
		t.Fatalf("password = %q, want app_pass", pass)
	}
}

func TestBuildDSNRejectsInvalidURI(t *testing.T) {
	_, err := BuildDSN(ConnConfig{URI: "http://[::1", Username: "u", Password: "p"})
	if err == nil {
		t.Fatalf("BuildDSN() error = nil, want error")
	}
	if !strings.Contains(err.Error(), "invalid uri") {
		t.Fatalf("BuildDSN() error = %q", err)
	}
}

func TestBuildDSNRejectsMissingScheme(t *testing.T) {
	_, err := BuildDSN(ConnConfig{URI: "//db.example.local/feedkit", Username: "u", Password: "p"})
	if err == nil {
		t.Fatalf("BuildDSN() error = nil, want error")
	}
	if !strings.Contains(err.Error(), "missing scheme") {
		t.Fatalf("BuildDSN() error = %q", err)
	}
}

func TestBuildDSNRejectsMissingHost(t *testing.T) {
	_, err := BuildDSN(ConnConfig{URI: "postgres:///feedkit", Username: "u", Password: "p"})
	if err == nil {
		t.Fatalf("BuildDSN() error = nil, want error")
	}
	if !strings.Contains(err.Error(), "missing host") {
		t.Fatalf("BuildDSN() error = %q", err)
	}
}

func TestOpenPropagatesOpenFailure(t *testing.T) {
	withPostgresPackageTestState(t)

	sqlOpen = func(_, _ string) (*sql.DB, error) {
		return nil, errors.New("open failed")
	}

	_, err := Open(context.Background(), ConnConfig{
		URI:      "postgres://db.example.local/feedkit",
		Username: "u",
		Password: "p",
	})
	if err == nil {
		t.Fatalf("Open() error = nil, want error")
	}
	if !strings.Contains(err.Error(), "open failed") {
		t.Fatalf("Open() error = %q", err)
	}
}

func TestOpenPropagatesPingFailure(t *testing.T) {
	withPostgresPackageTestState(t)

	const driverName = "feedkit_internal_postgres_ping_fail"
	registerPingTestDriver(driverName, errors.New("ping failed"))

	sqlOpen = func(_, _ string) (*sql.DB, error) {
		return sql.Open(driverName, "")
	}

	_, err := Open(context.Background(), ConnConfig{
		URI:      "postgres://db.example.local/feedkit",
		Username: "u",
		Password: "p",
	})
	if err == nil {
		t.Fatalf("Open() error = nil, want error")
	}
	if !strings.Contains(err.Error(), "ping failed") {
		t.Fatalf("Open() error = %q", err)
	}
}

var (
	pingDriverMu   sync.Mutex
	pingDriverSeen = map[string]bool{}
)

func registerPingTestDriver(name string, pingErr error) {
	pingDriverMu.Lock()
	defer pingDriverMu.Unlock()

	if pingDriverSeen[name] {
		return
	}
	sql.Register(name, &pingTestDriver{pingErr: pingErr})
	pingDriverSeen[name] = true
}

type pingTestDriver struct {
	pingErr error
}

func (d *pingTestDriver) Open(string) (driver.Conn, error) {
	return &pingTestConn{pingErr: d.pingErr}, nil
}

type pingTestConn struct {
	pingErr error
}

func (c *pingTestConn) Prepare(string) (driver.Stmt, error) {
	return nil, errors.New("not implemented")
}
func (c *pingTestConn) Close() error               { return nil }
func (c *pingTestConn) Begin() (driver.Tx, error)  { return nil, errors.New("not implemented") }
func (c *pingTestConn) Ping(context.Context) error { return c.pingErr }

func (c *pingTestConn) QueryContext(context.Context, string, []driver.NamedValue) (driver.Rows, error) {
	return &pingTestRows{}, nil
}

type pingTestRows struct{}

func (r *pingTestRows) Columns() []string         { return []string{"ok"} }
func (r *pingTestRows) Close() error              { return nil }
func (r *pingTestRows) Next([]driver.Value) error { return io.EOF }