// Copyright 2022 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 database

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"

	"golang.org/x/exp/maps"
	"golang.org/x/exp/slices"
	"golang.org/x/vuln/client"
	"golang.org/x/vulndb/internal/derrors"
)

// Write writes the contents of the Database to JSON files,
// following the specification in https://go.dev/security/vuln/database#api.
// path is the base path where the database will be written, and indent
// indicates if the JSON should be indented.
func (d *Database) Write(path string, indent bool) (err error) {
	defer derrors.Wrap(&err, "Database.Write(%q)", path)

	if err := os.MkdirAll(path, 0755); err != nil {
		return fmt.Errorf("failed to create directory %q: %s", path, err)
	}

	if err = d.writeIndex(path, indent); err != nil {
		return err
	}

	if err = d.writeAliasIndex(path, indent); err != nil {
		return err
	}

	if err = d.writeEntriesByModule(path, indent); err != nil {
		return err
	}

	if err = d.writeEntriesByID(path, indent); err != nil {
		return err
	}

	return nil
}

func WriteJSON(filename string, value any, indent bool) (err error) {
	defer derrors.Wrap(&err, "writeJSON(%s)", filename)

	j, err := jsonMarshal(value, indent)
	if err != nil {
		return err
	}
	return os.WriteFile(filename, j, 0644)
}

func jsonMarshal(v any, indent bool) ([]byte, error) {
	if indent {
		return json.MarshalIndent(v, "", "  ")
	}
	return json.Marshal(v)
}

func (d *Database) writeIndex(path string, indent bool) error {
	return WriteJSON(filepath.Join(path, indexFile), d.Index, indent)
}

func (d *Database) writeAliasIndex(path string, indent bool) error {
	return WriteJSON(filepath.Join(path, aliasesFile), d.IDsByAlias, indent)
}

func (d *Database) writeEntriesByModule(path string, indent bool) error {
	for module, entries := range d.EntriesByModule {
		epath, err := client.EscapeModulePath(module)
		if err != nil {
			return err
		}
		outPath := filepath.Join(path, epath)
		if err := os.MkdirAll(filepath.Dir(outPath), 0755); err != nil {
			return fmt.Errorf("failed to create directory %q: %s", filepath.Dir(outPath), err)
		}
		if err = WriteJSON(outPath+".json", entries, indent); err != nil {
			return err
		}
	}
	return nil
}

func (d *Database) writeEntriesByID(path string, indent bool) error {
	idDirPath := filepath.Join(path, idDirectory)
	if err := os.MkdirAll(idDirPath, 0755); err != nil {
		return fmt.Errorf("failed to create directory %q: %v", idDirPath, err)
	}
	// Write the entry files.
	for _, entry := range d.EntriesByID {
		if err := WriteJSON(filepath.Join(idDirPath, entry.ID+".json"), entry, indent); err != nil {
			return err
		}
	}
	idIndex := maps.Keys(d.EntriesByID)
	slices.Sort(idIndex)
	// Write the ID Index.
	return WriteJSON(filepath.Join(idDirPath, indexFile), idIndex, indent)
}