package main

import (
	"go/ast"
	"go/importer"
	"go/parser"
	"go/token"
	"go/types"
	"strings"
	"testing"
)

func TestExportedContractBoundaries(t *testing.T) {
	tests := []struct {
		name      string
		source    string
		wantError string
	}{
		{
			name: "leaked implementation type",
			source: `package facade
import "example.com/implementation"
func New() *implementation.State { return nil }
`,
			wantError: "exposes named type example.com/implementation.State",
		},
		{
			name: "alias to implementation type",
			source: `package facade
import "example.com/implementation"
type Alias = implementation.State
`,
			wantError: "exposes named type example.com/implementation.State",
		},
		{
			name: "callback leaks implementation type",
			source: `package facade
import "example.com/implementation"
type Callback func() *implementation.State
`,
			wantError: "exposes named type example.com/implementation.State",
		},
		{
			name: "generic constraint leaks implementation type",
			source: `package facade
import "example.com/implementation"
type Box[T interface{ Value() *implementation.State }] struct { value T }
`,
			wantError: "exposes named type example.com/implementation.State",
		},
		{
			name: "generic instantiation leaks implementation type",
			source: `package facade
import "example.com/implementation"
type Box[T any] struct { value T }
func New() Box[implementation.State] { return Box[implementation.State]{} }
`,
			wantError: "exposes named type example.com/implementation.State",
		},
		{
			name: "promoted implementation method",
			source: `package facade
import "example.com/implementation"
type state = implementation.State
type Handle struct { state }
`,
			wantError: "promotes method Promoted from example.com/implementation",
		},
		{
			name: "promoted pointer implementation method",
			source: `package facade
import "example.com/implementation"
type state = implementation.State
type Handle struct { state }
`,
			wantError: "promotes method PointerPromoted from example.com/implementation",
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			violations := checkFixture(t, test.source)
			if !strings.Contains(strings.Join(violations, "\n"), test.wantError) {
				t.Fatalf("checkExports() = %v, want an error containing %q", violations, test.wantError)
			}
		})
	}
}

func TestPrivateImplementationFieldAndSelectedStandardTypes(t *testing.T) {
	source := `package facade
import (
	"context"
	"example.com/implementation"
)
type Handle struct { state *implementation.State }
func Open(context.Context) *Handle { return nil }
`
	if violations := checkFixture(t, source); len(violations) != 0 {
		t.Fatalf("private implementation field and selected standard type were rejected: %v", violations)
	}
}

func TestActualRepositoryBoundaries(t *testing.T) {
	if err := checkRepository(t.Context(), "../.."); err != nil {
		t.Fatal(err)
	}
}

func TestInternalPackagesCannotImportPublicFacades(t *testing.T) {
	packages := []listedPackage{
		{ImportPath: modulePath + "/internal/operations", Imports: []string{modulePath}},
		{ImportPath: modulePath + "/cmd/releasekit/internal/cli", Imports: []string{modulePath + "/buildinfo"}},
		{ImportPath: modulePath},
		{ImportPath: modulePath + "/buildinfo"},
	}
	err := checkImportDirections(packages)
	if err == nil ||
		!strings.Contains(err.Error(), "internal package "+modulePath+"/internal/operations imports public or command package "+modulePath) ||
		!strings.Contains(err.Error(), "internal package "+modulePath+"/cmd/releasekit/internal/cli imports public or command package "+modulePath+"/buildinfo") {
		t.Fatalf("checkImportDirections() error = %v, want internal-to-facade violation", err)
	}
}

func TestRuntimeFacadeCannotDependOnExternalPackages(t *testing.T) {
	packages := []listedPackage{
		{ImportPath: modulePath + "/buildinfo", Imports: []string{"example.com/runtime"}},
		{ImportPath: "example.com/runtime"},
	}
	err := checkImportDirections(packages)
	if err == nil || !strings.Contains(err.Error(), "buildinfo depends on non-runtime package example.com/runtime") {
		t.Fatalf("checkImportDirections() error = %v, want runtime dependency violation", err)
	}
}

func checkFixture(t *testing.T, facadeSource string) []string {
	t.Helper()
	fset := token.NewFileSet()
	implementation := typecheck(t, fset, "example.com/implementation", `package implementation
type State struct{}
func (State) Promoted() {}
func (*State) PointerPromoted() {}
`)
	fixtureImporter := singlePackageImporter{path: "example.com/implementation", pkg: implementation}
	facade := typecheckWithImporter(t, fset, "example.com/facade", facadeSource, fixtureImporter)
	return checkExports(facade)
}

type singlePackageImporter struct {
	path string
	pkg  *types.Package
}

func (i singlePackageImporter) Import(path string) (*types.Package, error) {
	if path == i.path {
		return i.pkg, nil
	}
	return importer.Default().Import(path)
}

func typecheck(t *testing.T, fset *token.FileSet, path, source string) *types.Package {
	t.Helper()
	return typecheckWithImporter(t, fset, path, source, importer.Default())
}

func typecheckWithImporter(t *testing.T, fset *token.FileSet, path, source string, imports types.Importer) *types.Package {
	t.Helper()
	file, err := parser.ParseFile(fset, path+".go", source, 0)
	if err != nil {
		t.Fatal(err)
	}
	var errors []error
	config := types.Config{
		Importer: imports,
		Error: func(err error) {
			errors = append(errors, err)
		},
	}
	pkg, err := config.Check(path, fset, []*ast.File{file}, nil)
	if err != nil {
		t.Fatalf("typecheck %s: %v (%v)", path, err, errors)
	}
	return pkg
}