package cgo

import (
	"bytes"
	"flag"
	"fmt"
	"go/ast"
	"go/format"
	"go/parser"
	"go/token"
	"go/types"
	"io/ioutil"
	"path/filepath"
	"strings"
	"testing"
)

// Pass -update to go test to update the output of the test files.
var flagUpdate = flag.Bool("update", false, "Update images based on test output.")

func TestCGo(t *testing.T) {
	var cflags = []string{"--target=armv6m-none-eabi"}

	for _, name := range []string{"basic", "types"} {
		name := name // avoid a race condition
		t.Run(name, func(t *testing.T) {
			t.Parallel()

			// Read the AST in memory.
			path := filepath.Join("testdata", name+".go")
			fset := token.NewFileSet()
			f, err := parser.ParseFile(fset, path, nil, parser.ParseComments)
			if err != nil {
				t.Fatal("could not parse Go source file:", err)
			}

			// Process the AST with CGo.
			cgoAST, errs := Process([]*ast.File{f}, "testdata", fset, cflags)
			for _, err := range errs {
				t.Errorf("error during CGo processing: %v", err)
			}

			// Check the AST for type errors.
			hasTypeError := false
			config := types.Config{
				Error: func(err error) {
					t.Error("typecheck error:", err)
					hasTypeError = true
				},
				Importer: simpleImporter{},
				Sizes:    types.SizesFor("gccgo", "arm"),
			}
			_, err = config.Check("", fset, []*ast.File{f, cgoAST}, nil)
			if err != nil && !hasTypeError {
				// Only report errors when no type errors are found (an
				// unexpected condition).
				t.Error(err)
			}

			// Store the (formatted) output in a buffer. Format it, so it
			// becomes easier to read (and will hopefully change less with CGo
			// changes).
			buf := &bytes.Buffer{}
			err = format.Node(buf, fset, cgoAST)
			if err != nil {
				t.Errorf("could not write out CGo AST: %v", err)
			}
			actual := strings.Replace(string(buf.Bytes()), "\r\n", "\n", -1)

			// Read the file with the expected output, to compare against.
			outfile := filepath.Join("testdata", name+".out.go")
			expectedBytes, err := ioutil.ReadFile(outfile)
			if err != nil {
				t.Fatalf("could not read expected output: %v", err)
			}
			expected := strings.Replace(string(expectedBytes), "\r\n", "\n", -1)

			// Check whether the output is as expected.
			if expected != actual {
				// It is not. Test failed.
				if *flagUpdate {
					// Update the file with the expected data.
					err := ioutil.WriteFile(outfile, []byte(actual), 0666)
					if err != nil {
						t.Error("could not write updated output file:", err)
					}
					return
				}
				t.Errorf("output did not match:\n%s", string(actual))
			}
		})
	}
}

// simpleImporter implements the types.Importer interface, but only allows
// importing the unsafe package.
type simpleImporter struct {
}

// Import implements the Importer interface. For testing usage only: it only
// supports importing the unsafe package.
func (i simpleImporter) Import(path string) (*types.Package, error) {
	switch path {
	case "unsafe":
		return types.Unsafe, nil
	default:
		return nil, fmt.Errorf("importer not implemented for package %s", path)
	}
}