package task

import (
	"cmp"
	"context"
	"errors"
	"fmt"
	"io"
	"maps"
	"runtime/debug"
	"slices"
	"time"

	"github.com/dustin/go-humanize"

	"github.com/anchore/syft/internal"
	"github.com/anchore/syft/internal/archive"
	"github.com/anchore/syft/internal/bus"
	"github.com/anchore/syft/internal/log"
	"github.com/anchore/syft/internal/mimetype"
	"github.com/anchore/syft/internal/sbomsync"
	"github.com/anchore/syft/internal/unknown"
	"github.com/anchore/syft/syft/artifact"
	"github.com/anchore/syft/syft/cataloging"
	"github.com/anchore/syft/syft/cataloging/pkgcataloging"
	"github.com/anchore/syft/syft/event/monitor"
	"github.com/anchore/syft/syft/file"
	"github.com/anchore/syft/syft/pkg"
	"github.com/anchore/syft/syft/sbom"
)

const ArchiveCatalogerTaskName = "archive-cataloger"

// NewArchiveCatalogerTask returns a task that extracts every archive it finds, runs subPipeline
// against the archive's contents as a standalone filesystem, and records CONTAINS relationships
// from the archive to what was found inside it. It recurses into the archives it extracts up to
// cfg.MaxDepth; the task drops itself from subPipeline so that is the only recursion.
//
// exclusions are the scan's exclusion patterns, applied inside each archive. Returns nil when archive
// cataloging is disabled (MaxDepth == 0; negative means as deep as unboundedArchiveDepth).
func NewArchiveCatalogerTask(cfg cataloging.ArchiveSearchConfig, subPipeline []Task, exclusions []string) Task {
	return newArchiveCatalogerTask(cfg.MaxDepth, archiveLimits(cfg), subPipeline, exclusions)
}

// archiveLimits maps the configured limits onto the limiter's. Zero means the default, so the limiter's
// own zero (which forbids the resource) is not reachable from configuration.
func archiveLimits(cfg cataloging.ArchiveSearchConfig) archive.Limits {
	return archive.Limits{
		MaxMemoryBytes: cmp.Or(cfg.MaxMemoryBytes, int64(cataloging.DefaultArchiveMaxMemoryBytes)),
		MaxDiskBytes:   cmp.Or(cfg.MaxDiskBytes, int64(cataloging.DefaultArchiveMaxDiskBytes)),
	}
}

func newArchiveCatalogerTask(maxDepth int, limits archive.Limits, subPipeline []Task, exclusions []string) Task {
	if maxDepth == 0 {
		return nil
	}
	subPipeline = withoutArchiveCataloger(subPipeline)
	if len(subPipeline) == 0 {
		return nil
	}

	fn := func(ctx context.Context, resolver file.Resolver, builder sbomsync.Builder) error {
		// catalogers run once per archive, and each must report into the one progress row it owns
		ctx = bus.WithCatalogerTaskRegistry(ctx)

		c := &archiveCataloger{
			maxDepth:    maxDepth,
			subPipeline: subPipeline,
			limiter:     archive.NewLimiter(limits),
			exclusions:  archive.NewExclusions(exclusions),
			progress:    bus.StartCatalogerTask(ctx, archiveCatalogerProgressInfo(), -1, ""),
		}
		err := c.catalog(ctx, resolver, 0, builder)
		c.progress.AtomicStage.Set(fmt.Sprintf("%s archives", humanize.Comma(c.progress.Current())))
		c.progress.SetCompleted()
		c.logStats()
		return err
	}
	return NewTask(ArchiveCatalogerTaskName, fn, pkgcataloging.PackageTag, "archive")
}

func archiveCatalogerProgressInfo() monitor.GenericTask {
	return monitor.GenericTask{
		Title: monitor.Title{
			Default: "Archives",
		},
		ID:       ArchiveCatalogerTaskName,
		ParentID: monitor.TopLevelCatalogingTaskID,
	}
}

func withoutArchiveCataloger(tasks []Task) []Task {
	var out []Task
	for _, t := range tasks {
		if t == nil || t.Name() == ArchiveCatalogerTaskName {
			continue
		}
		out = append(out, t)
	}
	return out
}

type archiveCataloger struct {
	maxDepth    int
	subPipeline []Task
	limiter     *archive.Limiter
	exclusions  archive.Exclusions

	// progress is the one row for the whole walk: its count is how many archives have been entered
	progress *monitor.TaskProgress

	// ancestors are the digests of the archives the walk is currently inside. The walk is depth-first
	// and sequential, so this is a stack.
	ancestors []file.Digest

	// the archive that spent the longest on its own extraction and cataloging, excluding nested archives
	slowest     time.Duration
	slowestPath string
}

// logStats reports what the walk cost, once. The peaks are the most held against each limit at any
// one moment, comparable to the configured bounds.
func (c *archiveCataloger) logStats() {
	peakMemory, peakDisk := c.limiter.Peak()
	fields := []any{
		"archives", c.progress.Current(),
		"peak-memory", humanize.Bytes(uint64(peakMemory)),
		"peak-disk", humanize.Bytes(uint64(peakDisk)),
	}
	if c.slowestPath != "" {
		fields = append(fields, "slowest", c.slowestPath, "slowest-took", c.slowest.Round(time.Millisecond))
	}
	log.WithFields(fields...).Info("nested archive cataloging complete")
}

// unboundedArchiveDepth is the depth a negative MaxDepth stops at. No real nesting comes close, and a
// hostile archive (a zip quine, a recursive bomb) must still end.
const unboundedArchiveDepth = 16

// catalog processes every archive in the resolver, recursing into each up to maxDepth.
func (c *archiveCataloger) catalog(ctx context.Context, resolver file.Resolver, depth int, builder sbomsync.Builder) error {
	maxDepth := c.maxDepth
	if maxDepth < 0 {
		maxDepth = unboundedArchiveDepth
	}
	if depth >= maxDepth {
		return nil
	}
	var errs error
	for _, candidate := range c.discoverArchives(resolver) {
		if err := ctx.Err(); err != nil {
			return err
		}
		if err := c.processArchive(ctx, resolver, candidate, depth, builder); err != nil {
			errs = unknown.Append(errs, candidate.location, err)
		}
	}
	return errs
}

func (c *archiveCataloger) processArchive(ctx context.Context, parentResolver file.Resolver, candidate archiveCandidate, depth int, builder sbomsync.Builder) (err error) {
	// the decoders run on untrusted bytes; a panic in one costs this archive, not the scan
	defer func() {
		if r := recover(); r != nil {
			err = fmt.Errorf("panic while cataloging archive: %v at:\n%s", r, debug.Stack())
		}
	}()

	location := candidate.location
	content, err := parentResolver.FileContentsByLocation(location)
	if err != nil {
		return err
	}
	defer internal.CloseAndLogError(content, location.AccessPath)

	var archiveContent io.Reader = content
	if !candidate.sniffedAsArchive {
		var mayHide bool
		if archiveContent, mayHide = archive.MayHideAnAppendedArchive(content); !mayHide {
			return nil
		}
	}

	started := time.Now()

	// extracted files keep the filesystem ID of where the archive was found; the nesting chain is
	// carried separately as the archive path. The chain names real paths, not the link the archive was
	// reached by, so it is stable and joins to the archive's package location by prefix.
	archivePath := archive.VirtualPath(file.NewLocationFromCoordinates(location.Coordinates))
	extracted, err := archive.Extract(ctx, archiveContent, location.FileSystemID, archivePath, c.limiter, c.exclusions)
	if errors.Is(err, archive.ErrDiskLimitReached) {
		// nothing is released while this archive waits, so skip it rather than block the scan
		recordArchiveUnknown(builder, location.Coordinates, "archive skipped: its content would exceed the disk limit")
		return nil
	}
	if err != nil {
		return err
	}
	if extracted == nil {
		// a format with no extractor, or a candidate whose head only looked like an appended archive.
		// Logged rather than returned: an image can hold thousands of these
		log.WithFields("archive", archivePath, "sniffed-as-archive", candidate.sniffedAsArchive).
			Trace("no extractor could read this candidate; skipping")
		return nil
	}
	defer extracted.Cleanup()

	// an archive whose bytes match one it is nested in (a zip quine) would recurse forever
	if c.isAncestor(extracted.Digests) {
		recordArchiveUnknown(builder, location.Coordinates, "archive not cataloged: it is identical to an archive that contains it")
		return nil
	}
	c.ancestors = append(c.ancestors, extracted.Digests...)
	defer func() { c.ancestors = c.ancestors[:len(c.ancestors)-len(extracted.Digests)] }()

	if extracted.Truncated {
		recordArchiveUnknown(builder, location.Coordinates, "archive cataloged from part of its contents: extraction stopped at the configured memory or disk limit")
	}

	traversal := &archive.Traversal{Location: location, Digests: extracted.Digests}
	ctx = archive.WithTraversal(ctx, traversal)

	c.progress.Increment()
	scratch := c.runSubPipeline(ctx, extracted, location.Coordinates)
	mergeArchiveResults(location.Coordinates, scratch, builder)
	c.progress.AtomicStage.Set(fmt.Sprintf("%s archives (%s)", humanize.Comma(c.progress.Current()), archivePath))

	// self time stops before descending, so a containing archive is not charged for what it contains
	if took := time.Since(started); took > c.slowest {
		c.slowest, c.slowestPath = took, archivePath
	}

	return c.catalog(ctx, extracted, depth+1, builder)
}

func (c *archiveCataloger) isAncestor(digests []file.Digest) bool {
	for _, d := range digests {
		if slices.Contains(c.ancestors, d) {
			return true
		}
	}
	return false
}

func recordArchiveUnknown(builder sbomsync.Builder, coordinates file.Coordinates, reason string) {
	appendUnknowns(builder, ArchiveCatalogerTaskName, []unknown.CoordinateError{{Coordinates: coordinates, Reason: errors.New(reason)}})
}

// runSubPipeline runs every task against the resolver into a throwaway SBOM, so results can be
// attributed to the containing archive before merging into the shared SBOM.
//
// Failures are recorded as RunTask records them at the top level: errors carrying coordinates keep
// them, anything else is attributed to the archive. A failure never fails the archive or the scan.
func (c *archiveCataloger) runSubPipeline(ctx context.Context, resolver file.Resolver, archiveCoordinates file.Coordinates) *sbom.SBOM {
	scratch := &sbom.SBOM{Artifacts: sbom.Artifacts{Packages: pkg.NewCollection()}}
	scratchBuilder := sbomsync.NewBuilder(scratch)
	for _, t := range c.subPipeline {
		err := runTaskSafely(ctx, t, resolver, scratchBuilder)
		if err == nil {
			continue
		}
		log.WithFields("task", t.Name(), "error", err).Trace("archive sub-cataloger task reported an error")

		unknowns, remaining := unknown.ExtractCoordinateErrors(err)
		if remaining != nil {
			unknowns = append(unknowns, unknown.CoordinateError{Coordinates: archiveCoordinates, Reason: remaining})
		}
		appendUnknowns(scratchBuilder, t.Name(), unknowns)
	}
	return scratch
}

// archiveCandidate is one file the walk will try to open.
type archiveCandidate struct {
	location file.Location

	// sniffedAsArchive is true when the file's content types it as an archive. Such a file that cannot
	// be extracted is a broken archive and is reported; a file that is a candidate only by name is
	// passed over silently.
	sniffedAsArchive bool
}

// zipArchiveGlobs find files named like zip archives whose content did not sniff as one, such as a
// Spring Boot executable jar: a launcher script with a zip appended. The name only decides what gets
// opened; the end-of-central-directory record decides whether it is an archive.
//
// Globs rather than a MIME lookup, because asking for every executable, script and unrecognized file
// returned thousands of locations that were all discarded.
var zipArchiveGlobs = []string{
	"**/*.jar", "**/*.war", "**/*.ear", "**/*.par", "**/*.sar", "**/*.nar", "**/*.kar",
	"**/*.hpi", "**/*.jpi", "**/*.far", "**/*.rar", "**/*.zip", "**/*.apk", "**/*.aar",
	"**/*.egg", "**/*.whl", "**/*.lpkg", "**/*.zap", "**/*.exe",
}

// discoverArchives returns every file worth opening: those whose content is an archive, plus those
// named like a zip whose tail may still hold one.
func (c *archiveCataloger) discoverArchives(resolver file.Resolver) []archiveCandidate {
	archives, err := resolver.FilesByMIMEType(mimetype.ArchiveMIMETypeSet.List()...)
	if err != nil {
		log.WithFields("error", err).Debug("unable to list archive files for recursive cataloging")
		return nil
	}

	var candidates []archiveCandidate
	seen := map[file.Coordinates]int{}
	for _, loc := range archives {
		seen[loc.Coordinates] = len(candidates)
		candidates = append(candidates, archiveCandidate{location: loc, sniffedAsArchive: true})
	}

	namedLikeZips, err := resolver.FilesByGlob(zipArchiveGlobs...)
	if err != nil {
		log.WithFields("error", err).Debug("unable to list files that may carry an appended archive")
		return candidates
	}
	for _, loc := range namedLikeZips {
		if i, dup := seen[loc.Coordinates]; dup {
			// a MIME hit is the bare real path; the name it is reached by (a link such as
			// lib/dep.jar -> ../store/3f9a1c) is what name-based catalogers like java key off
			if prev := candidates[i].location; prev.AccessPath == "" || prev.AccessPath == prev.RealPath {
				candidates[i].location = loc
			}
			continue
		}
		seen[loc.Coordinates] = len(candidates)
		candidates = append(candidates, archiveCandidate{location: loc})
	}
	return candidates
}

// mergeArchiveResults copies the throwaway SBOM's packages, files and relationships into the shared
// SBOM, adding a CONTAINS relationship from the archive to everything found inside it.
func mergeArchiveResults(archiveCoordinates file.Coordinates, scratch *sbom.SBOM, builder sbomsync.Builder) {
	pkgs := scratch.Artifacts.Packages.Sorted()
	if len(pkgs) > 0 {
		builder.AddPackages(pkgs...)
	}

	if accessor, ok := builder.(sbomsync.Accessor); ok {
		accessor.WriteToSBOM(func(s *sbom.SBOM) {
			mergeFileArtifacts(&s.Artifacts, &scratch.Artifacts)
		})
	}

	var rels []artifact.Relationship
	for _, p := range pkgs {
		rels = append(rels, artifact.Relationship{From: archiveCoordinates, To: p, Type: artifact.ContainsRelationship})
	}
	for _, coordinates := range scratch.AllCoordinates() {
		rels = append(rels, artifact.Relationship{From: archiveCoordinates, To: coordinates, Type: artifact.ContainsRelationship})
	}
	rels = append(rels, scratch.Relationships...)
	if len(rels) > 0 {
		builder.AddRelationships(rels...)
	}
}

func mergeFileArtifacts(dst, src *sbom.Artifacts) {
	mergeInto(&dst.FileMetadata, src.FileMetadata)
	mergeInto(&dst.FileDigests, src.FileDigests)
	mergeInto(&dst.FileContents, src.FileContents)
	mergeInto(&dst.FileLicenses, src.FileLicenses)
	mergeInto(&dst.Executables, src.Executables)
	if len(src.Unknowns) > 0 && dst.Unknowns == nil {
		dst.Unknowns = map[file.Coordinates][]string{}
	}
	for coordinates, reasons := range src.Unknowns {
		dst.Unknowns[coordinates] = append(dst.Unknowns[coordinates], reasons...)
	}
}

func mergeInto[K comparable, V any](dst *map[K]V, src map[K]V) {
	if len(src) == 0 {
		return
	}
	if *dst == nil {
		*dst = make(map[K]V, len(src))
	}
	maps.Copy(*dst, src)
}