// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"flag"
	"fmt"
	"go/ast"
	"go/build"
	"go/parser"
	"go/scanner"
	"go/token"
	"io/ioutil"
	"os"
	"path/filepath"
	"runtime"
	"time"

	"golang.org/x/tools/go/gccgoimporter"
	_ "golang.org/x/tools/go/gcimporter"
	"golang.org/x/tools/go/types"
)

var (
	// main operation modes
	allFiles  = flag.Bool("a", false, "use all (incl. _test.go) files when processing a directory")
	allErrors = flag.Bool("e", false, "report all errors (not just the first 10)")
	verbose   = flag.Bool("v", false, "verbose mode")
	gccgo     = flag.Bool("gccgo", false, "use gccgoimporter instead of gcimporter")

	// debugging support
	sequential    = flag.Bool("seq", false, "parse sequentially, rather than in parallel")
	printAST      = flag.Bool("ast", false, "print AST (forces -seq)")
	printTrace    = flag.Bool("trace", false, "print parse trace (forces -seq)")
	parseComments = flag.Bool("comments", false, "parse comments (ignored unless -ast or -trace is provided)")
)

var (
	fset       = token.NewFileSet()
	errorCount = 0
	parserMode parser.Mode
	sizes      types.Sizes
)

func initParserMode() {
	if *allErrors {
		parserMode |= parser.AllErrors
	}
	if *printTrace {
		parserMode |= parser.Trace
	}
	if *parseComments && (*printAST || *printTrace) {
		parserMode |= parser.ParseComments
	}
}

func initSizes() {
	wordSize := 8
	maxAlign := 8
	switch build.Default.GOARCH {
	case "386", "arm":
		wordSize = 4
		maxAlign = 4
		// add more cases as needed
	}
	sizes = &types.StdSizes{WordSize: int64(wordSize), MaxAlign: int64(maxAlign)}
}

func usage() {
	fmt.Fprintln(os.Stderr, "usage: gotype [flags] [path ...]")
	flag.PrintDefaults()
	os.Exit(2)
}

func report(err error) {
	scanner.PrintError(os.Stderr, err)
	if list, ok := err.(scanner.ErrorList); ok {
		errorCount += len(list)
		return
	}
	errorCount++
}

// parse may be called concurrently
func parse(filename string, src interface{}) (*ast.File, error) {
	if *verbose {
		fmt.Println(filename)
	}
	file, err := parser.ParseFile(fset, filename, src, parserMode) // ok to access fset concurrently
	if *printAST {
		ast.Print(fset, file)
	}
	return file, err
}

func parseStdin() (*ast.File, error) {
	src, err := ioutil.ReadAll(os.Stdin)
	if err != nil {
		return nil, err
	}
	return parse("<standard input>", src)
}

func parseFiles(filenames []string) ([]*ast.File, error) {
	files := make([]*ast.File, len(filenames))

	if *sequential {
		for i, filename := range filenames {
			var err error
			files[i], err = parse(filename, nil)
			if err != nil {
				return nil, err // leave unfinished goroutines hanging
			}
		}
	} else {
		type parseResult struct {
			file *ast.File
			err  error
		}

		out := make(chan parseResult)
		for _, filename := range filenames {
			go func(filename string) {
				file, err := parse(filename, nil)
				out <- parseResult{file, err}
			}(filename)
		}

		for i := range filenames {
			res := <-out
			if res.err != nil {
				return nil, res.err // leave unfinished goroutines hanging
			}
			files[i] = res.file
		}
	}

	return files, nil
}

func parseDir(dirname string) ([]*ast.File, error) {
	ctxt := build.Default
	pkginfo, err := ctxt.ImportDir(dirname, 0)
	if _, nogo := err.(*build.NoGoError); err != nil && !nogo {
		return nil, err
	}
	filenames := append(pkginfo.GoFiles, pkginfo.CgoFiles...)
	if *allFiles {
		filenames = append(filenames, pkginfo.TestGoFiles...)
	}

	// complete file names
	for i, filename := range filenames {
		filenames[i] = filepath.Join(dirname, filename)
	}

	return parseFiles(filenames)
}

func getPkgFiles(args []string) ([]*ast.File, error) {
	if len(args) == 0 {
		// stdin
		file, err := parseStdin()
		if err != nil {
			return nil, err
		}
		return []*ast.File{file}, nil
	}

	if len(args) == 1 {
		// possibly a directory
		path := args[0]
		info, err := os.Stat(path)
		if err != nil {
			return nil, err
		}
		if info.IsDir() {
			return parseDir(path)
		}
	}

	// list of files
	return parseFiles(args)
}

func checkPkgFiles(files []*ast.File) {
	type bailout struct{}
	conf := types.Config{
		FakeImportC: true,
		Error: func(err error) {
			if !*allErrors && errorCount >= 10 {
				panic(bailout{})
			}
			report(err)
		},
		Sizes: sizes,
	}
	if *gccgo {
		var inst gccgoimporter.GccgoInstallation
		inst.InitFromDriver("gccgo")
		conf.Import = inst.GetImporter(nil, nil)
	}

	defer func() {
		switch p := recover().(type) {
		case nil, bailout:
			// normal return or early exit
		default:
			// re-panic
			panic(p)
		}
	}()

	const path = "pkg" // any non-empty string will do for now
	conf.Check(path, fset, files, nil)
}

func printStats(d time.Duration) {
	fileCount := 0
	lineCount := 0
	fset.Iterate(func(f *token.File) bool {
		fileCount++
		lineCount += f.LineCount()
		return true
	})

	fmt.Printf(
		"%s (%d files, %d lines, %d lines/s)\n",
		d, fileCount, lineCount, int64(float64(lineCount)/d.Seconds()),
	)
}

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU()) // remove this once runtime is smarter

	flag.Usage = usage
	flag.Parse()
	if *printAST || *printTrace {
		*sequential = true
	}
	initParserMode()
	initSizes()

	start := time.Now()

	files, err := getPkgFiles(flag.Args())
	if err != nil {
		report(err)
		os.Exit(2)
	}

	checkPkgFiles(files)
	if errorCount > 0 {
		os.Exit(2)
	}

	if *verbose {
		printStats(time.Since(start))
	}
}