package commands

import (
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"github.com/git-lfs/git-lfs/v3/errors"
	"github.com/git-lfs/git-lfs/v3/git/gitattr"
	"github.com/git-lfs/git-lfs/v3/git/githistory"
	"github.com/git-lfs/git-lfs/v3/lfs"
	"github.com/git-lfs/git-lfs/v3/tasklog"
	"github.com/git-lfs/git-lfs/v3/tools"
	"github.com/git-lfs/git-lfs/v3/tools/humanize"
	"github.com/git-lfs/git-lfs/v3/tr"
	"github.com/git-lfs/gitobj/v2"
	"github.com/spf13/cobra"
)

type migrateInfoPointersType int

const (
	migrateInfoPointersFollow   = migrateInfoPointersType(iota)
	migrateInfoPointersNoFollow = migrateInfoPointersType(iota)
	migrateInfoPointersIgnore   = migrateInfoPointersType(iota)
)

var (
	// migrateInfoTopN is a flag given to the git-lfs-migrate(1) subcommand
	// 'info' which specifies how many info entries to show by default.
	migrateInfoTopN int

	// migrateInfoAboveFmt is a flag given to the git-lfs-migrate(1)
	// subcommand 'info' specifying a human-readable string threshold of
	// filesize before entries are counted.
	migrateInfoAboveFmt string
	// migrateInfoAbove is the number of bytes parsed from the above
	// migrateInfoAboveFmt flag.
	migrateInfoAbove uint64

	// migrateInfoUnitFmt is a flag given to the git-lfs-migrate(1)
	// subcommand 'info' specifying a human-readable string of units with
	// which to display the number of bytes.
	migrateInfoUnitFmt string
	// migrateInfoUnit is the number of bytes in the unit given as
	// migrateInfoUnitFmt.
	migrateInfoUnit uint64

	// migrateInfoPointers is an option given to the git-lfs-migrate(1)
	// subcommand 'info' specifying how to treat Git LFS pointers.
	migrateInfoPointers string
	// migrateInfoPointersMode is the Git LFS pointer treatment mode
	// parsed from migrateInfoPointers.
	migrateInfoPointersMode migrateInfoPointersType
)

func migrateInfoCommand(cmd *cobra.Command, args []string) {
	l := tasklog.NewLogger(os.Stderr,
		tasklog.ForceProgress(cfg.ForceProgress()),
	)

	db, err := getObjectDatabase()
	if err != nil {
		ExitWithError(err)
	}
	defer db.Close()

	rewriter := getHistoryRewriter(cmd, db, l)

	exts := make(map[string]*MigrateInfoEntry)

	above, err := humanize.ParseBytes(migrateInfoAboveFmt)
	if err != nil {
		ExitWithError(errors.Wrap(err, tr.Tr.Get("cannot parse --above=<n>")))
	}

	if u := cmd.Flag("unit"); u.Changed {
		unit, err := humanize.ParseByteUnit(u.Value.String())
		if err != nil {
			ExitWithError(errors.Wrap(err, tr.Tr.Get("cannot parse --unit=<unit>")))
		}

		migrateInfoUnit = unit
	}

	pointers := cmd.Flag("pointers")
	if pointers.Changed {
		switch pointers.Value.String() {
		case "follow":
			migrateInfoPointersMode = migrateInfoPointersFollow
		case "no-follow":
			migrateInfoPointersMode = migrateInfoPointersNoFollow
		case "ignore":
			migrateInfoPointersMode = migrateInfoPointersIgnore
		default:
			ExitWithError(errors.Errorf(tr.Tr.Get("Unsupported --pointers option value")))
		}
	}

	if migrateFixup {
		include, exclude := getIncludeExcludeArgs(cmd)
		if include != nil || exclude != nil {
			ExitWithError(errors.Errorf(tr.Tr.Get("Cannot use --fixup with --include, --exclude")))
		}
		if pointers.Changed && migrateInfoPointersMode != migrateInfoPointersIgnore {
			ExitWithError(errors.Errorf(tr.Tr.Get("Cannot use --fixup with --pointers=%s", pointers.Value.String())))
		}
		migrateInfoPointersMode = migrateInfoPointersIgnore
	}

	migrateInfoAbove = above
	pointersInfoEntry := &MigrateInfoEntry{Qualifier: "LFS Objects", Separate: true}
	var fixups *gitattr.Tree

	migrate(args, rewriter, l, &githistory.RewriteOptions{
		BlobFn: func(path string, b *gitobj.Blob) (*gitobj.Blob, error) {
			var entry *MigrateInfoEntry
			var size int64
			var p *lfs.Pointer
			var err error

			if migrateFixup {
				if filepath.Base(path) == ".gitattributes" {
					return b, nil
				}

				var ok bool
				attrs := fixups.Applied(path)
				for _, attr := range attrs {
					if attr.K == "filter" {
						ok = attr.V == "lfs"
					}
				}
				if !ok {
					return b, nil
				}
			}

			if migrateInfoPointersMode != migrateInfoPointersNoFollow {
				p, err = lfs.DecodePointerFromBlob(b)
			}
			if p != nil && err == nil {
				if migrateInfoPointersMode == migrateInfoPointersIgnore {
					return b, nil
				}
				entry = pointersInfoEntry
				size = p.Size
			} else {
				entry = findEntryByExtension(exts, path)
				size = b.Size
			}

			entry.Total++

			if size > int64(migrateInfoAbove) {
				entry.TotalAbove++
				entry.BytesAbove += size
			}

			return b, nil
		},

		TreePreCallbackFn: func(path string, t *gitobj.Tree) error {
			if migrateFixup {
				if path == "/" {
					var err error

					fixups, err = gitattr.New(db, t)
					if err != nil {
						return err
					}
				}
				return nil
			}

			for _, e := range t.Entries {
				if strings.ToLower(e.Name) == ".gitattributes" && e.Type() == gitobj.BlobObjectType {
					if e.IsLink() {
						return errors.Errorf("migrate: %s", tr.Tr.Get("expected '.gitattributes' to be a file, got a symbolic link"))
					} else {
						break
					}
				}
			}

			return nil
		},
	})
	l.Close()

	entries := EntriesBySize(MapToEntries(exts))
	entries = removeEmptyEntries(entries)
	sort.Sort(sort.Reverse(entries))

	migrateInfoTopN = tools.ClampInt(migrateInfoTopN, 0, len(entries))

	entries = entries[:migrateInfoTopN]
	if pointersInfoEntry.Total > 0 {
		entries = append(entries, pointersInfoEntry)
	}

	entries.Print(os.Stdout)
}

// MigrateInfoEntry represents a tuple of filetype to bytes and entry count
// above and below a threshold.
type MigrateInfoEntry struct {
	// Qualifier is the filepath's extension.
	Qualifier string
	// Separate indicates if the entry should be printed separately.
	Separate bool

	// BytesAbove is total size of all files above a given threshold.
	BytesAbove int64
	// TotalAbove is the count of all files above a given size threshold.
	TotalAbove int64
	// Total is the count of all files.
	Total int64
}

// findEntryByExtension finds or creates an entry from the given map that
// corresponds with the given path's file extension (or the path's file name
// if there is no file extension).
func findEntryByExtension(exts map[string]*MigrateInfoEntry, path string) *MigrateInfoEntry {
	ext := fmt.Sprintf("*%s", filepath.Ext(path))

	// If extension exists, group all items under extension,
	// else just use the file name.
	var groupName string
	if len(ext) > 1 {
		groupName = ext
	} else {
		groupName = filepath.Base(path)
	}

	entry := exts[groupName]
	if entry == nil {
		entry = &MigrateInfoEntry{Qualifier: groupName}
		exts[groupName] = entry
	}

	return entry
}

// MapToEntries creates a set of `*MigrateInfoEntry`'s for a given map of
// filepath extensions to file size in bytes.
func MapToEntries(exts map[string]*MigrateInfoEntry) []*MigrateInfoEntry {
	entries := make([]*MigrateInfoEntry, 0, len(exts))
	for _, entry := range exts {
		entries = append(entries, entry)
	}

	return entries
}

// removeEmptyEntries removes `*MigrateInfoEntry`'s for which no matching file
// is above the given threshold "--above".
func removeEmptyEntries(entries []*MigrateInfoEntry) []*MigrateInfoEntry {
	nz := make([]*MigrateInfoEntry, 0, len(entries))
	for _, e := range entries {
		if e.TotalAbove > 0 {
			nz = append(nz, e)
		}
	}

	return nz
}

// EntriesBySize is an implementation of sort.Interface that sorts a set of
// `*MigrateInfoEntry`'s
type EntriesBySize []*MigrateInfoEntry

// Len returns the total length of the set of `*MigrateInfoEntry`'s.
func (e EntriesBySize) Len() int { return len(e) }

// Less returns the whether or not the MigrateInfoEntry given at `i` takes up
// less total size than the MigrateInfoEntry given at `j`.
func (e EntriesBySize) Less(i, j int) bool {
	if e[i].BytesAbove == e[j].BytesAbove {
		return e[i].Qualifier > e[j].Qualifier
	} else {
		return e[i].BytesAbove < e[j].BytesAbove
	}
}

// Swap swaps the entries given at i, j.
func (e EntriesBySize) Swap(i, j int) { e[i], e[j] = e[j], e[i] }

// Print formats the `*MigrateInfoEntry`'s in the set and prints them to the
// given io.Writer, "to", returning "n" the number of bytes written, and any
// error, if one occurred.
func (e EntriesBySize) Print(to io.Writer) (int, error) {
	if len(e) == 0 {
		return 0, nil
	}

	extensions := make([]string, 0, len(e))
	separateFlags := make([]bool, 0, len(e))
	sizes := make([]string, 0, len(e))
	stats := make([]string, 0, len(e))
	percentages := make([]string, 0, len(e))

	for _, entry := range e {
		bytesAbove := uint64(entry.BytesAbove)
		above := entry.TotalAbove
		total := entry.Total
		percentAbove := 100 * (float64(above) / float64(total))

		var size string
		if migrateInfoUnit > 0 {
			size = humanize.FormatBytesUnit(bytesAbove, migrateInfoUnit)
		} else {
			size = humanize.FormatBytes(bytesAbove)
		}

		// TRANSLATORS: The strings here are intended to have the same
		// display width including spaces, so please insert trailing
		// spaces as necessary for your language.
		stat := tr.Tr.GetN(
			"%d/%d file ",
			"%d/%d files",
			int(total),
			above,
			total,
		)

		percentage := fmt.Sprintf("%.0f%%", percentAbove)

		extensions = append(extensions, entry.Qualifier)
		separateFlags = append(separateFlags, entry.Separate)
		sizes = append(sizes, size)
		stats = append(stats, stat)
		percentages = append(percentages, percentage)
	}

	extensions = tools.Ljust(extensions)
	sizes = tools.Ljust(sizes)
	stats = tools.Rjust(stats)
	percentages = tools.Rjust(percentages)

	output := make([]string, 0, len(e))
	for i := 0; i < len(e); i++ {
		extension := extensions[i]
		size := sizes[i]
		stat := stats[i]
		percentage := percentages[i]

		line := strings.Join([]string{extension, size, stat, percentage}, "\t")

		if i > 0 && separateFlags[i] {
			output = append(output, "")
		}
		output = append(output, line)
	}

	return fmt.Fprintln(to, strings.Join(output, "\n"))
}