package importer

import (
	"context"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"github.com/jackc/pgx/v5/pgtype"

	"git.fabledsword.com/bvandeusen/minstrel/internal/acquire"
	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
	"git.fabledsword.com/bvandeusen/minstrel/internal/downloader"
	"git.fabledsword.com/bvandeusen/minstrel/internal/library"
	"git.fabledsword.com/bvandeusen/minstrel/internal/release"
)

// Importing an upgrade (M502 #5524): a better copy of an album the library
// holds. Each file is matched to the track it would replace, by recording
// and then by disc and track. It replaces that track when the track is a
// video rip or the new file is a better tier; otherwise the old track stays.
// A file with no track to replace fills a gap, as any import does.
//
// The new copy is filed before the old one goes. On the old file's own path
// it takes the path in one rename and the row carries on; at a new path it
// is scanned in as a track of its own and the old track is folded into it
// (library.ReplaceTrack), so likes, plays and playlist entries carry over.

// OldTrack is a library track an upgrade may replace.
type OldTrack struct {
	ID          pgtype.UUID
	Path        string
	Recording   string
	Disc, Track int
	Format      string
	Bytes       int64
	Ms          int64
	Rip         bool
}

// Tier is the old track's tier, estimated as the upgrade check estimates
// an album's; ok is false for a format the ladder cannot place.
func (o OldTrack) Tier() (release.Tier, bool) {
	return release.TierOfFile(o.Format, release.FileKbps(o.Bytes, o.Ms))
}

// What an upgrade does with one placement.
const (
	stepPlace     = "place"     // no track to replace: fills a gap
	stepReplace   = "replace"   // replaces Old from a new path
	stepOverwrite = "overwrite" // replaces Old on its own path
	stepKeep      = "keep"      // Old is as good: left as it is
)

type upgradeStep struct {
	Placement int
	Action    string
	Old       int // index into olds, or -1
}

// planUpgrade matches each placement to the track it would replace and
// decides what to do with it. newTiers is each placement's tier.
func planUpgrade(plan []Placement, newTiers []release.Tier, olds []OldTrack) []upgradeStep {
	used := make([]bool, len(olds))
	match := make([]int, len(plan))
	for i := range match {
		match[i] = -1
	}
	for i, pl := range plan {
		if pl.Recording == "" {
			continue
		}
		for j, o := range olds {
			if !used[j] && o.Recording == pl.Recording {
				match[i], used[j] = j, true
				break
			}
		}
	}
	for i, pl := range plan {
		if match[i] >= 0 || pl.Track <= 0 {
			continue
		}
		for j, o := range olds {
			if !used[j] && o.Track == pl.Track && max(o.Disc, 1) == max(pl.Disc, 1) {
				match[i], used[j] = j, true
				break
			}
		}
	}
	steps := make([]upgradeStep, len(plan))
	for i, pl := range plan {
		j := match[i]
		steps[i] = upgradeStep{Placement: i, Old: j, Action: stepPlace}
		if j < 0 {
			continue
		}
		o := olds[j]
		oldTier, _ := o.Tier()
		better := release.Rank(newTiers[i]) > release.Rank(oldTier)
		switch {
		case !o.Rip && !better:
			steps[i].Action = stepKeep
		case filepath.Clean(pl.Dest) == filepath.Clean(o.Path):
			steps[i].Action = stepOverwrite
		default:
			steps[i].Action = stepReplace
		}
	}
	return steps
}

// fileTier estimates a downloaded file's tier from its size and length, the
// way the library's are estimated, so the two compare like for like. A file
// that cannot be measured takes the release's tier.
func fileTier(f File, fallback release.Tier) release.Tier {
	if info, err := os.Stat(f.Path); err == nil && f.LengthMs > 0 {
		if t, ok := release.TierOfFile(filepath.Ext(f.Path), release.FileKbps(info.Size(), int64(f.LengthMs))); ok {
			return t
		}
	}
	return fallback
}

func oldTracks(rows []dbq.ListUpgradeTracksRow) []OldTrack {
	out := make([]OldTrack, 0, len(rows))
	for _, r := range rows {
		o := OldTrack{ID: r.ID, Path: r.FilePath, Disc: int(r.Disc), Format: r.FileFormat,
			Bytes: r.FileSize, Ms: int64(r.DurationMs), Rip: r.SourceVerdict != nil && *r.SourceVerdict == "suspect"}
		if r.Mbid != nil {
			o.Recording = *r.Mbid
		}
		if r.TrackNumber != nil {
			o.Track = int(*r.TrackNumber)
		}
		out = append(out, o)
	}
	return out
}

// placeUpgrade files an accepted upgrade, replacing the tracks it betters.
func (im *Importer) placeUpgrade(ctx context.Context, q *dbq.Queries, g dbq.Grab, d downloader.Driver, w Want,
	e *Edition, files []File, plan []Placement, v Verdict, det Detail, record recordFunc) string {
	rows, err := q.ListUpgradeTracks(ctx, w.AlbumID)
	if err != nil {
		return record(StateWaiting, "Couldn't read the album's tracks: "+err.Error(), "", det, 0, "")
	}
	olds := oldTracks(rows)
	grabTier := release.Tier(g.Quality)
	newTiers := make([]release.Tier, len(plan))
	for i, pl := range plan {
		newTiers[i] = fileTier(files[pl.File], grabTier)
	}
	steps := planUpgrade(plan, newTiers, olds)
	heldRec, heldPos, err := im.held(ctx, q, w, plan)
	if err != nil {
		return record(StateWaiting, "Couldn't read what the library holds: "+err.Error(), "", det, 0, "")
	}

	type swap struct {
		old  OldTrack
		dest string
	}
	var (
		placed  []string // every file written, for the scan
		swaps   []swap
		inPlace []OldTrack
		failed  []string
	)
	for _, st := range steps {
		pl := plan[st.Placement]
		if st.Action == stepKeep {
			det.Skipped++
			continue
		}
		if st.Action == stepPlace && ((pl.Recording != "" && heldRec[pl.Recording]) || heldPos[[2]int{pl.Disc, pl.Track}]) {
			det.Skipped++
			continue
		}
		tags := Tags{Title: pl.Title, Artist: w.Artist, Album: w.Title, AlbumArtist: w.Artist, Year: w.Year,
			Disc: pl.Disc, Discs: pl.Discs, Track: pl.Track, Tracks: pl.Tracks,
			GroupMBID: w.GroupMBID, RecordingMBID: pl.Recording, ArtistMBID: w.ArtistMBID}
		if e != nil {
			tags.ReleaseMBID = e.MBID
		}
		src := files[pl.File].Path
		var tagged bool
		if st.Action == stepOverwrite {
			tagged, err = Overwrite(ctx, src, pl.Dest, tags)
		} else {
			tagged, err = Place(ctx, src, pl.Dest, tags)
		}
		switch {
		case errors.Is(err, ErrOccupied):
			det.Skipped++
			continue
		case err != nil:
			// Each replacement stands alone: the old track stays where a
			// copy failed, and the rest go ahead.
			failed = append(failed, pl.Title)
			im.logger.Warn("import: copy an upgrade into the library", "grab", g.Name, "dest", pl.Dest, "err", err)
			continue
		}
		placed = append(placed, pl.Dest)
		if !tagged {
			det.Untagged++
		}
		switch st.Action {
		case stepOverwrite:
			inPlace = append(inPlace, olds[st.Old])
		case stepReplace:
			swaps = append(swaps, swap{old: olds[st.Old], dest: pl.Dest})
		}
	}
	det.Placed = len(placed)

	if len(placed) == 0 {
		why := fmt.Sprintf("Nothing in it is better than the copy of %s you have, so nothing was imported.", w.Title)
		if len(failed) > 0 {
			return record(StateFailed, fmt.Sprintf("Copying into the library failed for %s.", strings.Join(failed, ", ")),
				"", det, 0, "")
		}
		// Set aside, so the weekly search doesn't take it again.
		if err := acquire.NewMemory(im.pool).Block(ctx, dbq.BlockReleaseParams{
			InfoHash: g.InfoHash, Name: g.Name, Reason: acquire.BlockImport, Detail: why, WantID: g.WantID,
		}); err != nil {
			im.logger.Warn("import: set the release aside", "grab", g.Name, "err", err)
		}
		if err := q.MarkWantSearched(ctx, g.WantID); err != nil {
			im.logger.Warn("import: mark the want searched", "grab", g.Name, "err", err)
		}
		im.removeFromClient(ctx, d, g)
		return record(StateHeld, why, StateHeld, det, 0, "")
	}

	if _, err := im.Scanner.ScanFiles(ctx, placed); err != nil {
		im.logger.Warn("import: scan the new files", "grab", g.Name, "err", err)
	}
	for _, o := range inPlace {
		if o.Rip {
			if err := q.ClearTrackSourceVerdict(ctx, o.ID); err != nil {
				im.logger.Warn("import: release a replaced rip", "path", o.Path, "err", err)
			}
		}
	}
	replaced, kept := len(inPlace), 0
	for _, s := range swaps {
		nt, err := q.GetTrackByPath(ctx, s.dest)
		if err != nil {
			kept++
			im.logger.Warn("import: find the new track", "path", s.dest, "err", err)
			continue
		}
		moved, err := library.ReplaceTrack(ctx, im.pool, im.logger, im.DataDir, s.old.ID, nt.ID)
		if err != nil {
			// The old file stays; the duplicate sweep finds the two copies.
			kept++
			im.logger.Warn("import: replace the old track", "old", s.old.Path, "new", s.dest, "err", err)
			continue
		}
		replaced++
		im.logger.Info("import: replaced a track with a better copy", "old", s.old.Path, "new", s.dest,
			"play_events", moved.PlayEvents, "likes", moved.Likes, "playlist_entries", moved.PlaylistEntries)
	}

	// The want holds the album the new tracks are in, once the old album row
	// has none left.
	var album pgtype.UUID
	if left, err := q.ListUpgradeTracks(ctx, w.AlbumID); err == nil && len(left) == 0 {
		if nt, err := q.GetTrackByPath(ctx, placed[0]); err == nil {
			album = nt.AlbumID
		}
	}
	if err := q.FinishUpgrade(ctx, dbq.FinishUpgradeParams{ID: g.WantID, AlbumID: album}); err != nil {
		im.logger.Warn("import: finish the upgrade", "grab", g.Name, "err", err)
	}
	if err := q.MarkWantSearched(ctx, g.WantID); err != nil {
		im.logger.Warn("import: mark the want searched", "grab", g.Name, "err", err)
	}

	dest := filepath.Dir(placed[0])
	if e != nil && e.Media() > 1 {
		dest = filepath.Dir(dest)
	}
	reason := fmt.Sprintf("Replaced %s of %s with a better copy.", tracks(replaced), w.Title)
	if added := len(placed) - replaced - kept; added > 0 {
		reason += fmt.Sprintf(" Added %s it was missing.", tracks(added))
	}
	if det.Skipped > 0 {
		reason += fmt.Sprintf(" %s already as good left as they were.", tracks(det.Skipped))
	}
	if kept > 0 {
		reason += fmt.Sprintf(" %s couldn't be removed, so both copies are in the library.", tracks(kept))
	}
	if len(failed) > 0 {
		reason += fmt.Sprintf(" Copying failed for %s; those stay as they were.", strings.Join(failed, ", "))
	}
	if det.Untagged > 0 {
		reason += fmt.Sprintf(" %s copied with their own tags: ffmpeg could not rewrite them.", tracks(det.Untagged))
	}
	return record(StateImported, reason+" "+v.Reason, StateImported, det, len(placed), dest)
}