// Copyright 2018 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 modcmd

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"

	"cmd/go/internal/base"
	"cmd/go/internal/modload"
	"cmd/go/internal/module"
)

func runVendor() {
	pkgs := modload.LoadVendor()

	vdir := filepath.Join(modload.ModRoot, "vendor")
	if err := os.RemoveAll(vdir); err != nil {
		base.Fatalf("go vendor: %v", err)
	}

	modpkgs := make(map[module.Version][]string)
	for _, pkg := range pkgs {
		m := modload.PackageModule(pkg)
		if m == modload.Target {
			continue
		}
		modpkgs[m] = append(modpkgs[m], pkg)
	}

	var buf bytes.Buffer
	for _, m := range modload.BuildList()[1:] {
		if pkgs := modpkgs[m]; len(pkgs) > 0 {
			repl := ""
			if r := modload.Replacement(m); r.Path != "" {
				repl = " => " + r.Path
				if r.Version != "" {
					repl += " " + r.Version
				}
			}
			fmt.Fprintf(&buf, "# %s %s%s\n", m.Path, m.Version, repl)
			if *modV {
				fmt.Fprintf(os.Stderr, "# %s %s%s\n", m.Path, m.Version, repl)
			}
			for _, pkg := range pkgs {
				fmt.Fprintf(&buf, "%s\n", pkg)
				if *modV {
					fmt.Fprintf(os.Stderr, "%s\n", pkg)
				}
				vendorPkg(vdir, pkg)
			}
		}
	}
	if buf.Len() == 0 {
		fmt.Fprintf(os.Stderr, "go: no dependencies to vendor\n")
		return
	}
	if err := ioutil.WriteFile(filepath.Join(vdir, "modules.txt"), buf.Bytes(), 0666); err != nil {
		base.Fatalf("go vendor: %v", err)
	}
}

func vendorPkg(vdir, pkg string) {
	realPath := modload.ImportMap(pkg)
	if realPath != pkg && modload.ImportMap(realPath) != "" {
		fmt.Fprintf(os.Stderr, "warning: %s imported as both %s and %s; making two copies.\n", realPath, realPath, pkg)
	}

	dst := filepath.Join(vdir, pkg)
	src := modload.PackageDir(realPath)
	if src == "" {
		fmt.Fprintf(os.Stderr, "internal error: no pkg for %s -> %s\n", pkg, realPath)
	}
	copyDir(dst, src, matchNonTest)
	if m := modload.PackageModule(realPath); m.Path != "" {
		copyMetadata(m.Path, realPath, dst, src)
	}
}

type metakey struct {
	modPath string
	dst     string
}

var copiedMetadata = make(map[metakey]bool)

// copyMetadata copies metadata files from parents of src to parents of dst,
// stopping after processing the src parent for modPath.
func copyMetadata(modPath, pkg, dst, src string) {
	for parent := 0; ; parent++ {
		if copiedMetadata[metakey{modPath, dst}] {
			break
		}
		copiedMetadata[metakey{modPath, dst}] = true
		if parent > 0 {
			copyDir(dst, src, matchMetadata)
		}
		if modPath == pkg {
			break
		}
		pkg = filepath.Dir(pkg)
		dst = filepath.Dir(dst)
		src = filepath.Dir(src)
	}
}

// metaPrefixes is the list of metadata file prefixes.
// Vendoring copies metadata files from parents of copied directories.
// Note that this list could be arbitrarily extended, and it is longer
// in other tools (such as godep or dep). By using this limited set of
// prefixes and also insisting on capitalized file names, we are trying
// to nudge people toward more agreement on the naming
// and also trying to avoid false positives.
var metaPrefixes = []string{
	"AUTHORS",
	"CONTRIBUTORS",
	"COPYLEFT",
	"COPYING",
	"COPYRIGHT",
	"LEGAL",
	"LICENSE",
	"NOTICE",
	"PATENTS",
}

// matchMetadata reports whether info is a metadata file.
func matchMetadata(info os.FileInfo) bool {
	name := info.Name()
	for _, p := range metaPrefixes {
		if strings.HasPrefix(name, p) {
			return true
		}
	}
	return false
}

// matchNonTest reports whether info is any non-test file (including non-Go files).
func matchNonTest(info os.FileInfo) bool {
	return !strings.HasSuffix(info.Name(), "_test.go")
}

// copyDir copies all regular files satisfying match(info) from src to dst.
func copyDir(dst, src string, match func(os.FileInfo) bool) {
	files, err := ioutil.ReadDir(src)
	if err != nil {
		base.Fatalf("go vendor: %v", err)
	}
	if err := os.MkdirAll(dst, 0777); err != nil {
		base.Fatalf("go vendor: %v", err)
	}
	for _, file := range files {
		if file.IsDir() || !file.Mode().IsRegular() || !match(file) {
			continue
		}
		r, err := os.Open(filepath.Join(src, file.Name()))
		if err != nil {
			base.Fatalf("go vendor: %v", err)
		}
		w, err := os.Create(filepath.Join(dst, file.Name()))
		if err != nil {
			base.Fatalf("go vendor: %v", err)
		}
		if _, err := io.Copy(w, r); err != nil {
			base.Fatalf("go vendor: %v", err)
		}
		r.Close()
		if err := w.Close(); err != nil {
			base.Fatalf("go vendor: %v", err)
		}
	}
}