// Copyright 2023 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 cmd

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"go/token"
	"io/fs"
	"os"
	"path/filepath"
	"reflect"
	"runtime"
	"strings"
	"time"

	"golang.org/x/tools/gopls/internal/filecache"
	"golang.org/x/tools/gopls/internal/protocol"
	protocolcommand "golang.org/x/tools/gopls/internal/protocol/command"
	"golang.org/x/tools/gopls/internal/settings"
	"golang.org/x/tools/gopls/internal/util/bug"
	versionpkg "golang.org/x/tools/gopls/internal/version"
	"golang.org/x/tools/internal/event"
)

type stats struct {
	app *application

	Anon bool `flag:"anon" help:"hide any fields that may contain user names, file names, or source code"`
}

func (s *stats) Name() string      { return "stats" }
func (r *stats) Parent() string    { return r.app.Name() }
func (s *stats) Usage() string     { return "" }
func (s *stats) ShortHelp() string { return "print workspace statistics" }

func (s *stats) DetailedHelp(f *flag.FlagSet) {
	fmt.Fprint(f.Output(), `
Load the workspace for the current directory, and output a JSON summary of
workspace information relevant to performance. As a side effect, this command
populates the gopls file cache for the current workspace.

By default, this command may include output that refers to the location or
content of user code. When the -anon flag is set, fields that may refer to user
code are hidden.

Example:
  $ gopls stats -anon
`)
	printFlagDefaults(f)
}

func (s *stats) Run(ctx context.Context, args ...string) error {
	// stats does not work with -remote yet.
	// Other sessions on the daemon may interfere with results.
	// Additionally, the type assertions in below only work if progress
	// notifications bypass jsonrpc2 serialization.
	// TODO(hyangah): support remote mode by fetching server-side
	// statistics and avoiding hangs during InitialWorkspaceLoad.
	if s.app.Remote != "" {
		return commandLineErrorf("stats does not currently support remote mode")
	}

	if !s.app.Verbose {
		event.SetExporter(nil) // don't log errors to stderr
	}

	stats := statsJSON{
		GOOS:             runtime.GOOS,
		GOARCH:           runtime.GOARCH,
		GOPLSCACHE:       os.Getenv("GOPLSCACHE"),
		GoVersion:        runtime.Version(),
		GoplsVersion:     versionpkg.Version(),
		GOPACKAGESDRIVER: os.Getenv("GOPACKAGESDRIVER"),
	}

	opts := s.app.options
	s.app.options = func(o *settings.Options) {
		if opts != nil {
			opts(o)
		}
		o.VerboseWorkDoneProgress = true
	}

	// do executes a timed section of the stats command.

	do := func(name string, f func() error) (time.Duration, error) {
		start := time.Now()
		fmt.Fprintf(os.Stderr, "%-30s", name+"...")
		if err := f(); err != nil {
			return time.Since(start), err
		}
		d := time.Since(start)
		fmt.Fprintf(os.Stderr, "done (%v)\n", d)
		return d, nil
	}

	var cli *client
	iwlDuration, err := do("Initializing workspace", func() (err error) {
		cli, _, err = s.app.connect(ctx)
		if err != nil {
			return err
		}
		select {
		case <-cli.iwlDone:
		case <-ctx.Done():
			return ctx.Err()
		}
		return nil
	})
	if err != nil {
		return err
	}
	defer cli.terminate(ctx)

	stats.InitialWorkspaceLoadDuration = fmt.Sprint(iwlDuration)

	// Gather bug reports produced by any process using
	// this executable and persisted in the cache.
	do("Gathering bug reports", func() error {
		stats.CacheDir, stats.BugReports = filecache.BugReports()
		if stats.BugReports == nil {
			stats.BugReports = []bug.Bug{} // non-nil for JSON
		}
		return nil
	})

	if _, err := do("Querying memstats", func() error {
		memStats, err := executeCommand(ctx, cli.server, &protocol.Command{
			Command: protocolcommand.MemStats.String(),
		})
		if err != nil {
			return err
		}
		stats.MemStats = memStats.(protocolcommand.MemStatsResult)
		return nil
	}); err != nil {
		return err
	}

	if _, err := do("Querying workspace stats", func() error {
		wsStats, err := executeCommand(ctx, cli.server, &protocol.Command{
			Command: protocolcommand.WorkspaceStats.String(),
		})
		if err != nil {
			return err
		}
		stats.WorkspaceStats = wsStats.(protocolcommand.WorkspaceStatsResult)
		return nil
	}); err != nil {
		return err
	}

	if _, err := do("Collecting directory info", func() error {
		var err error
		stats.DirStats, err = findDirStats()
		if err != nil {
			return err
		}
		return nil
	}); err != nil {
		return err
	}

	// Filter JSON output to fields that are consistent with s.Anon.
	okFields := make(map[string]any)
	{
		v := reflect.ValueOf(stats)
		t := v.Type()
		for i := 0; i < t.NumField(); i++ {
			f := t.Field(i)
			if !token.IsExported(f.Name) {
				continue
			}
			vf := v.FieldByName(f.Name)
			if s.Anon && f.Tag.Get("anon") != "ok" && !vf.IsZero() {
				// Fields that can be served with -anon must be explicitly marked as OK.
				// But, if it's zero value, it's ok to print.
				continue
			}
			okFields[f.Name] = vf.Interface()
		}
	}
	data, err := json.MarshalIndent(okFields, "", "  ")
	if err != nil {
		return err
	}

	os.Stdout.Write(data)
	fmt.Println()
	return nil
}

// statsJSON holds information extracted from a gopls session in the current
// workspace.
//
// Fields that should be printed with the -anon flag should be explicitly
// marked as `anon:"ok"`. Only fields that cannot refer to user files or code
// should be marked as such.
type statsJSON struct {
	GOOS, GOARCH                 string `anon:"ok"`
	GOPLSCACHE                   string
	GoVersion                    string `anon:"ok"`
	GoplsVersion                 string `anon:"ok"`
	GOPACKAGESDRIVER             string
	InitialWorkspaceLoadDuration string `anon:"ok"` // in time.Duration string form
	CacheDir                     string
	BugReports                   []bug.Bug
	MemStats                     protocolcommand.MemStatsResult       `anon:"ok"`
	WorkspaceStats               protocolcommand.WorkspaceStatsResult `anon:"ok"`
	DirStats                     dirStats                             `anon:"ok"`
}

type dirStats struct {
	Files         int
	TestdataFiles int
	GoFiles       int
	ModFiles      int
	Dirs          int
}

// findDirStats collects information about the current directory and its
// subdirectories.
func findDirStats() (dirStats, error) {
	var ds dirStats
	err := filepath.WalkDir(".", func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if d.IsDir() {
			ds.Dirs++
		} else {
			ds.Files++
			slashed := filepath.ToSlash(path)
			switch {
			case strings.Contains(slashed, "/testdata/") || strings.HasPrefix(slashed, "testdata/"):
				ds.TestdataFiles++
			case strings.HasSuffix(path, ".go"):
				ds.GoFiles++
			case strings.HasSuffix(path, ".mod"):
				ds.ModFiles++
			}
		}
		return nil
	})
	return ds, err
}
