// Copyright 2021 Google LLC
//
// 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.

package main

import (
	"bytes"
	"flag"
	"fmt"
	"io"
	"io/fs"
	"os"
	"path/filepath"
	"strings"

	"android/soong/tools/compliance"
)

var (
	outputFile  = flag.String("o", "-", "Where to write the bill of materials. (default stdout)")
	stripPrefix = newMultiString("strip_prefix", "Prefix to remove from paths. i.e. path to root (multiple allowed)")

	failNoneRequested = fmt.Errorf("\nNo license metadata files requested")
	failNoLicenses    = fmt.Errorf("No licenses found")
)

type context struct {
	stdout      io.Writer
	stderr      io.Writer
	rootFS      fs.FS
	stripPrefix []string
}

func (ctx context) strip(installPath string) string {
	for _, prefix := range ctx.stripPrefix {
		if strings.HasPrefix(installPath, prefix) {
			p := strings.TrimPrefix(installPath, prefix)
			if 0 == len(p) {
				continue
			}
			return p
		}
	}
	return installPath
}

func init() {
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, `Usage: %s {options} file.meta_lic {file.meta_lic...}

Outputs a bill of materials. i.e. the list of installed paths.

Options:
`, filepath.Base(os.Args[0]))
		flag.PrintDefaults()
	}
}

// newMultiString creates a flag that allows multiple values in an array.
func newMultiString(name, usage string) *multiString {
	var f multiString
	flag.Var(&f, name, usage)
	return &f
}

// multiString implements the flag `Value` interface for multiple strings.
type multiString []string

func (ms *multiString) String() string     { return strings.Join(*ms, ", ") }
func (ms *multiString) Set(s string) error { *ms = append(*ms, s); return nil }

func main() {
	flag.Parse()

	// Must specify at least one root target.
	if flag.NArg() == 0 {
		flag.Usage()
		os.Exit(2)
	}

	if len(*outputFile) == 0 {
		flag.Usage()
		fmt.Fprintf(os.Stderr, "must specify file for -o; use - for stdout\n")
		os.Exit(2)
	} else {
		dir, err := filepath.Abs(filepath.Dir(*outputFile))
		if err != nil {
			fmt.Fprintf(os.Stderr, "cannot determine path to %q: %s\n", *outputFile, err)
			os.Exit(1)
		}
		fi, err := os.Stat(dir)
		if err != nil {
			fmt.Fprintf(os.Stderr, "cannot read directory %q of %q: %s\n", dir, *outputFile, err)
			os.Exit(1)
		}
		if !fi.IsDir() {
			fmt.Fprintf(os.Stderr, "parent %q of %q is not a directory\n", dir, *outputFile)
			os.Exit(1)
		}
	}

	var ofile io.Writer
	ofile = os.Stdout
	if *outputFile != "-" {
		ofile = &bytes.Buffer{}
	}

	ctx := &context{ofile, os.Stderr, os.DirFS("."), *stripPrefix}

	err := billOfMaterials(ctx, flag.Args()...)
	if err != nil {
		if err == failNoneRequested {
			flag.Usage()
		}
		fmt.Fprintf(os.Stderr, "%s\n", err.Error())
		os.Exit(1)
	}
	if *outputFile != "-" {
		err := os.WriteFile(*outputFile, ofile.(*bytes.Buffer).Bytes(), 0666)
		if err != nil {
			fmt.Fprintf(os.Stderr, "could not write output to %q: %s\n", *outputFile, err)
			os.Exit(1)
		}
	}
	os.Exit(0)
}

// billOfMaterials implements the bom utility.
func billOfMaterials(ctx *context, files ...string) error {
	// Must be at least one root file.
	if len(files) < 1 {
		return failNoneRequested
	}

	// Read the license graph from the license metadata files (*.meta_lic).
	licenseGraph, err := compliance.ReadLicenseGraph(ctx.rootFS, ctx.stderr, files)
	if err != nil {
		return fmt.Errorf("Unable to read license metadata file(s) %q: %v\n", files, err)
	}
	if licenseGraph == nil {
		return failNoLicenses
	}

	// rs contains all notice resolutions.
	rs := compliance.ResolveNotices(licenseGraph)

	ni, err := compliance.IndexLicenseTexts(ctx.rootFS, licenseGraph, rs)
	if err != nil {
		return fmt.Errorf("Unable to read license text file(s) for %q: %v\n", files, err)
	}

	for path := range ni.InstallPaths() {
		fmt.Fprintln(ctx.stdout, ctx.strip(path))
	}
	return nil
}
