package main

import (
	"slices"
	"testing"
)

// Signature hashes shared by the smoke-test records.
const (
	f1Head = "f1h"
	f1Tail = "f1t"
	f2Head = "f2h"
	f2Tail = "f2t"
)

// smokeTreeRecs mirrors the README smoke-test tree layout: /d/t1 and
// /d/t2 are identical, /d/t3 differs from them only by one filename.
func smokeTreeRecs() []scanRec {
	return []scanRec{
		{size: 3000, head: f1Head, tail: f1Tail, path: "/d/t1/f1"},
		{size: 100, head: f2Head, tail: f2Tail, path: "/d/t1/sub/f2"},
		{size: 3000, head: f1Head, tail: f1Tail, path: "/d/t2/f1"},
		{size: 100, head: f2Head, tail: f2Tail, path: "/d/t2/sub/f2"},
		{size: 3000, head: f1Head, tail: f1Tail, path: "/d/t3/f1"},
		{size: 100, head: f2Head, tail: f2Tail, path: "/d/t3/sub/f2renamed"},
	}
}

// nodeByPath finds the directory node with the given path.
func nodeByPath(t *testing.T, dirs []*treeNode, path string) *treeNode {
	t.Helper()

	for _, d := range dirs {
		if d.path == path {
			return d
		}
	}

	t.Fatalf("no directory node with path %q", path)

	return nil
}

// groupPaths flattens tree groups into their member path lists.
func groupPaths(groups [][]*treeNode) [][]string {
	out := make([][]string, 0, len(groups))
	for _, g := range groups {
		paths := make([]string, 0, len(g))
		for _, n := range g {
			paths = append(paths, n.path)
		}

		out = append(out, paths)
	}

	return out
}

func TestBuildHierarchyCounts(t *testing.T) {
	t.Parallel()

	super, dirs := buildHierarchy(smokeTreeRecs())
	super.compute()

	d := nodeByPath(t, dirs, "/d")
	if d.fileCount != 6 || d.totalSize != 9300 {
		t.Errorf("/d: fileCount %d size %d, want 6 9300",
			d.fileCount, d.totalSize)
	}

	t1 := nodeByPath(t, dirs, "/d/t1")
	if t1.fileCount != 2 || t1.totalSize != 3100 {
		t.Errorf("/d/t1: fileCount %d size %d, want 2 3100",
			t1.fileCount, t1.totalSize)
	}

	sub := nodeByPath(t, dirs, "/d/t1/sub")
	if sub.fileCount != 1 || sub.totalSize != 100 {
		t.Errorf("/d/t1/sub: fileCount %d size %d, want 1 100",
			sub.fileCount, sub.totalSize)
	}
}

func TestTreeDigests(t *testing.T) {
	t.Parallel()

	super, dirs := buildHierarchy(smokeTreeRecs())
	super.compute()

	t1 := nodeByPath(t, dirs, "/d/t1")
	t2 := nodeByPath(t, dirs, "/d/t2")
	t3 := nodeByPath(t, dirs, "/d/t3")

	if t1.digest != t2.digest {
		t.Error("identical trees /d/t1 and /d/t2 have different digests")
	}

	// t3 differs only in a filename; names are part of the digest.
	if t1.digest == t3.digest {
		t.Error("/d/t3 digest equals /d/t1 despite a renamed file")
	}

	sub1 := nodeByPath(t, dirs, "/d/t1/sub")
	sub3 := nodeByPath(t, dirs, "/d/t3/sub")

	if sub1.digest == sub3.digest {
		t.Error("subdirs with differently-named files share a digest")
	}
}

func TestTreeDigestContentSensitivity(t *testing.T) {
	t.Parallel()

	const sharedTail = "same"

	recs := []scanRec{
		{size: 10, head: sharedTail, tail: sharedTail, path: "/r/a/f"},
		{size: 10, head: "DIFF", tail: sharedTail, path: "/r/b/f"},
	}

	super, dirs := buildHierarchy(recs)
	super.compute()

	a := nodeByPath(t, dirs, "/r/a")
	b := nodeByPath(t, dirs, "/r/b")

	if a.digest == b.digest {
		t.Error("trees with different file content share a digest")
	}
}

func TestCollectTreeGroupsMaximal(t *testing.T) {
	t.Parallel()

	super, dirs := buildHierarchy(smokeTreeRecs())
	super.compute()

	groups := collectTreeGroups(dirs, super)

	want := [][]string{{"/d/t1", "/d/t2"}}
	if got := groupPaths(groups); !slices.EqualFunc(got, want,
		slices.Equal) {
		t.Fatalf("groups = %v, want %v", got, want)
	}

	// The /d/t1/sub vs /d/t2/sub group must be suppressed as implied
	// by its parents' group; the winning group reports one copy's
	// recursive totals.
	if groups[0][0].fileCount != 2 || groups[0][0].totalSize != 3100 {
		t.Errorf("group totals: %d files %d bytes, want 2 3100",
			groups[0][0].fileCount, groups[0][0].totalSize)
	}
}

func TestCollectTreeGroupsDeterministic(t *testing.T) {
	t.Parallel()

	recs := smokeTreeRecs()

	super, dirs := buildHierarchy(recs)
	super.compute()

	forward := groupPaths(collectTreeGroups(dirs, super))

	reversed := slices.Clone(recs)
	slices.Reverse(reversed)

	superR, dirsR := buildHierarchy(reversed)
	superR.compute()

	backward := groupPaths(collectTreeGroups(dirsR, superR))
	if !slices.EqualFunc(forward, backward, slices.Equal) {
		t.Fatalf("output depends on record order: %v vs %v",
			forward, backward)
	}
}

func TestCollectTreeGroupsSiblings(t *testing.T) {
	t.Parallel()

	// Identical sibling dirs share a parent, so their group cannot be
	// implied by a parent group and must be reported.
	recs := []scanRec{
		{size: 10, head: "h", tail: "t", path: "/p/x1/f"},
		{size: 10, head: "h", tail: "t", path: "/p/x2/f"},
	}

	super, dirs := buildHierarchy(recs)
	super.compute()

	got := groupPaths(collectTreeGroups(dirs, super))

	want := [][]string{{"/p/x1", "/p/x2"}}
	if !slices.EqualFunc(got, want, slices.Equal) {
		t.Fatalf("groups = %v, want %v", got, want)
	}
}

func TestCollectTreeGroupsDifferingParents(t *testing.T) {
	t.Parallel()

	// /p/a and /q/b contain identical x subtrees, but /p/a has an
	// extra file, so the parents' digests differ and the x group must
	// be reported.
	recs := []scanRec{
		{size: 10, head: "h", tail: "t", path: "/p/a/x/f"},
		{size: 99, head: "e", tail: "e", path: "/p/a/extra"},
		{size: 10, head: "h", tail: "t", path: "/q/b/x/f"},
	}

	super, dirs := buildHierarchy(recs)
	super.compute()

	got := groupPaths(collectTreeGroups(dirs, super))

	want := [][]string{{"/p/a/x", "/q/b/x"}}
	if !slices.EqualFunc(got, want, slices.Equal) {
		t.Fatalf("groups = %v, want %v", got, want)
	}
}