// Copyright 2018 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// +build ignore

package main

import (
	"fmt"
	"go/ast"
	"go/format"
	"go/parser"
	"go/token"
	"io/ioutil"
	"os"
	"path/filepath"
	"runtime"
	"strings"

	"golang.org/x/tools/go/ast/astutil"
)

func run() error {
	dir := filepath.Join(runtime.GOROOT(), "src", "image", "png")

	files, err := ioutil.ReadDir(dir)
	if err != nil {
		return err
	}

	for _, f := range files {
		if f.IsDir() {
			continue
		}
		if strings.HasSuffix(f.Name(), "_test.go") {
			continue
		}

		in, err := os.Open(filepath.Join(dir, f.Name()))
		if err != nil {
			return err
		}
		defer in.Close()

		out, err := os.Create("stdlib" + f.Name())
		if err != nil {
			return err
		}
		defer out.Close()

		// TODO: Remove call of RegisterDecoder

		data, err := ioutil.ReadAll(in)
		if err != nil {
			return err
		}
		fset := token.NewFileSet()
		tree, err := parser.ParseFile(fset, "", string(data), parser.ParseComments)
		if err != nil {
			return err
		}

		astutil.Apply(tree, func(c *astutil.Cursor) bool {
			stmt, ok := c.Node().(*ast.ExprStmt)
			if !ok {
				return true
			}
			call, ok := stmt.X.(*ast.CallExpr)
			if !ok {
				return true
			}
			s, ok := call.Fun.(*ast.SelectorExpr)
			if !ok {
				return true
			}
			receiver, ok := s.X.(*ast.Ident)
			if !ok {
				return true
			}
			// Delete registering PNG format.
			if receiver.Name == "image" && s.Sel.Name == "RegisterFormat" {
				c.Delete()
			}
			return true
		}, nil)

		fmt.Fprintln(out, "// Code generated by gen.go. DO NOT EDIT")
		fmt.Fprintln(out)
		format.Node(out, fset, tree)
	}
	return nil
}

func main() {
	if err := run(); err != nil {
		panic(err)
	}
}