package gormlog_test

import (
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"io/fs"
	"os"
	"path/filepath"
	"strings"
	"testing"

	"github.com/stretchr/testify/require"
)

// isRowProducer reports whether name is GORM's Row or database/sql's
// QueryRow or QueryRowContext, which return a *sql.Row whose Scan is
// database/sql's and not (*gorm.DB).Scan. GORM's Rows is not listed:
// it also returns an error, so Scan is never called on its result
// directly. It matches the method name only and resolves no types, so
// a repo-local method with one of these names that returns *gorm.DB
// gets past it: Scan on that method's result is not reported.
func isRowProducer(name string) bool {
	switch name {
	case "Row", "QueryRow", "QueryRowContext":
		return true
	default:
		return false
	}
}

// receiverIsRowHandle reports whether x is syntactically a call to a
// row producer, which is the only receiver form this check accepts for
// a Scan.
func receiverIsRowHandle(x ast.Expr) bool {
	call, ok := x.(*ast.CallExpr)
	if !ok {
		return false
	}

	sel, ok := call.Fun.(*ast.SelectorExpr)
	if !ok {
		return false
	}

	return isRowProducer(sel.Sel.Name)
}

// unguardedScans returns the position of every Scan call in file whose
// receiver is not a call to a row producer. It fails closed: any other
// receiver — a local variable, a struct field, a call to any other
// method — is reported rather than assumed safe.
//
// It sees only calls written x.Scan(...). A method value, f := db.Scan
// followed by f(&v), is out of scope: Scan is never the called
// expression there, and nobody writes a query that way by accident,
// which is the mistake this check exists to catch.
func unguardedScans(
	fset *token.FileSet, file *ast.File,
) []token.Position {
	var found []token.Position

	ast.Inspect(file, func(n ast.Node) bool {
		call, ok := n.(*ast.CallExpr)
		if !ok {
			return true
		}

		sel, ok := call.Fun.(*ast.SelectorExpr)
		if !ok || sel.Sel.Name != "Scan" {
			return true
		}

		if !receiverIsRowHandle(sel.X) {
			found = append(found, fset.Position(sel.Sel.Pos()))
		}

		return true
	})

	return found
}

// moduleRoot walks up from the working directory to the directory
// holding go.mod.
func moduleRoot(t *testing.T) string {
	t.Helper()

	dir, err := os.Getwd()
	require.NoError(t, err)

	for {
		_, statErr := os.Stat(filepath.Join(dir, "go.mod"))
		if statErr == nil {
			return dir
		}

		parent := filepath.Dir(dir)
		require.NotEqual(t, parent, dir, "no go.mod above %s", dir)

		dir = parent
	}
}

// skipDir reports whether a directory holds no source this check
// governs.
func skipDir(name string) bool {
	switch name {
	case ".git", "bin", "node_modules", "testdata":
		return true
	default:
		return false
	}
}

// walkNonTestGo parses every non-test .go file under root. It returns
// the directories, relative to root, it parsed a file in, along with
// every unguarded Scan it found.
func walkNonTestGo(t *testing.T, root string) (map[string]bool, []string) {
	t.Helper()

	walked := map[string]bool{}

	var hits []string

	fset := token.NewFileSet()

	require.NoError(t, filepath.WalkDir(
		root,
		func(path string, d fs.DirEntry, err error) error {
			if err != nil {
				return err
			}

			if d.IsDir() {
				if skipDir(d.Name()) {
					return fs.SkipDir
				}

				return nil
			}

			if !isNonTestGo(d.Name()) {
				return nil
			}

			file, err := parser.ParseFile(fset, path, nil, 0)
			if err != nil {
				return err
			}

			dir, err := filepath.Rel(root, filepath.Dir(path))
			if err != nil {
				return err
			}

			walked[dir] = true

			for _, pos := range unguardedScans(fset, file) {
				hits = append(hits, relPosition(root, pos))
			}

			return nil
		},
	))

	return walked, hits
}

// isNonTestGo reports whether a file name is Go source this check
// governs.
func isNonTestGo(name string) bool {
	return strings.HasSuffix(name, ".go") &&
		!strings.HasSuffix(name, "_test.go")
}

// relPosition renders pos with its path relative to root, so a failure
// names the file the way the repository does.
func relPosition(root string, pos token.Position) string {
	name := pos.Filename

	rel, err := filepath.Rel(root, name)
	if err == nil {
		name = rel
	}

	return fmt.Sprintf("%s:%d:%d", name, pos.Line, pos.Column)
}

// TestGormScanIsNeverCalledOutsideTests keeps (*gorm.DB).Scan out of
// non-test code.
//
// It is the one statement path (*Logger).ParamsFilter does not reach:
// Scan swaps GORM's own trace recorder in for the adapter, and that
// recorder does not implement gorm.ParamsFilter, so the statement is
// logged with its values interpolated. The package comment states the
// limit; this fails when someone adds a call site anyway.
//
// Test files are not governed: what a test binds is fixture data.
func TestGormScanIsNeverCalledOutsideTests(t *testing.T) {
	t.Parallel()

	root := moduleRoot(t)
	walked, offenders := walkNonTestGo(t, root)

	// The module's packages are static, templates, and every directory
	// directly under cmd and internal. Each holds non-test code, so one
	// the walk parsed nothing in was skipped, and a Scan there would
	// pass unseen.
	packages := []string{"static", "templates"}

	for _, parent := range []string{"cmd", "internal"} {
		entries, err := os.ReadDir(filepath.Join(root, parent))
		require.NoError(t, err)

		for _, entry := range entries {
			if !entry.IsDir() {
				continue
			}

			packages = append(packages, filepath.Join(parent, entry.Name()))
		}
	}

	for _, dir := range packages {
		require.True(
			t, walked[dir],
			"the walk parsed no non-test .go file in %s", dir,
		)
	}

	require.Empty(
		t, offenders,
		"Scan called on a receiver this check cannot show is a "+
			"database/sql row handle. (*gorm.DB).Scan logs the "+
			"statement with its bound values interpolated — use "+
			"Find, Pluck, or Raw(...).Row().Scan instead. A "+
			"database/sql Scan reached through a variable is "+
			"reported too; write it as <producer>().Scan rather "+
			"than widening this check.",
	)
}

// scanGuardCase is one planted snippet and whether the check above
// should report it.
type scanGuardCase struct {
	name string
	body string
	want int
}

// scanGuardCases covers each receiver form unguardedScans names, plus
// each row producer isRowProducer lets through. Each body is valid Go
// inside plantedFile.
func scanGuardCases() []scanGuardCase {
	return []scanGuardCase{
		{"local variable", "q := gdb.Raw(\"SELECT 1\")\n\tq.Scan(&v)", 1},
		{"struct field", `s.db.Scan(&v)`, 1},
		{"gorm chain", `gdb.Raw("SELECT 1").Scan(&v)`, 1},
		{
			"sql rows in a variable",
			"rows, _ := gdb.Raw(\"SELECT 1\").Rows()\n\trows.Scan(&v)",
			1,
		},
		{"gorm Row", `gdb.Raw("SELECT 1").Row().Scan(&v)`, 0},
		{"sql QueryRow", `sqlDB.QueryRow("SELECT 1").Scan(&v)`, 0},
		{
			"sql QueryRowContext",
			`sqlDB.QueryRowContext(ctx, "SELECT 1").Scan(&v)`,
			0,
		},
		{"unrelated call", `gdb.Find(&v)`, 0},
	}
}

// plantedFile wraps one case body in a function that declares every
// name the bodies use, so each body is the Go it stands for. The result
// is parsed, never compiled.
const plantedFile = `package p

import (
	"context"
	"database/sql"

	"gorm.io/gorm"
)

type store struct{ db *gorm.DB }

func f(ctx context.Context, gdb *gorm.DB, sqlDB *sql.DB, s store) {
	var v int

	%s
}
`

// TestScanGuard_ReportsPlantedCalls proves the check fires. Without it
// a detector that matched nothing would satisfy the walk above no
// matter what the tree contained.
func TestScanGuard_ReportsPlantedCalls(t *testing.T) {
	t.Parallel()

	for _, tc := range scanGuardCases() {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			fset := token.NewFileSet()
			src := fmt.Sprintf(plantedFile, tc.body)

			file, err := parser.ParseFile(
				fset, tc.name+".go", src, 0,
			)
			require.NoError(t, err)

			require.Len(t, unguardedScans(fset, file), tc.want)
		})
	}
}