// SPDX-License-Identifier: GPL-3.0-or-later

package apply

import (
	"os"
	"path/filepath"
	"slices"
	"strings"
	"testing"
	"time"

	"krino/internal/plan"
	"krino/internal/scan"
	"krino/internal/trash"
)

// chainFor builds a Chain whose File describes path as it is on disk now, so
// the executor's "changed since plan" check passes.
func chainFor(t *testing.T, root, rel string, steps ...plan.Step) plan.Chain {
	t.Helper()
	p := filepath.Join(root, rel)
	fi, err := os.Stat(p)
	if err != nil {
		t.Fatal(err)
	}
	return plan.Chain{
		File:  scan.File{Path: p, Rel: rel, Name: filepath.Base(rel), Size: fi.Size(), ModTime: fi.ModTime(), Mode: fi.Mode()},
		Steps: steps,
	}
}

func TestChainRunsStepsInOrder(t *testing.T) {
	root := t.TempDir()
	write(t, filepath.Join(root, "x.pdf"), "content", 0o644)
	c := chainFor(t, root, "x.pdf",
		plan.Step{Kind: plan.Copy, Rule: "backup", Src: filepath.Join(root, "x.pdf"), Dst: filepath.Join(root, "B", "x.pdf")},
		plan.Step{Kind: plan.Move, Rule: "acme", Src: filepath.Join(root, "x.pdf"), Dst: filepath.Join(root, "W", "x.pdf")},
	)
	got := Chain(c)
	if len(got) != 2 || got[0].Status != "ok" || got[1].Status != "ok" {
		t.Fatalf("results = %+v", got)
	}
	if b, err := os.ReadFile(filepath.Join(root, "B", "x.pdf")); err != nil || string(b) != "content" {
		t.Errorf("the copy is missing: %q %v", b, err)
	}
	if b, err := os.ReadFile(filepath.Join(root, "W", "x.pdf")); err != nil || string(b) != "content" {
		t.Errorf("the move did not arrive: %q %v", b, err)
	}
	if _, err := os.Stat(filepath.Join(root, "x.pdf")); !os.IsNotExist(err) {
		t.Error("the original survived the move")
	}
	if len(got[0].Made) == 0 {
		t.Error("the created directory was not recorded in Made")
	}
	if got[1].Size != int64(len("content")) {
		t.Errorf("Size = %d, want the size at Dst afterwards", got[1].Size)
	}
}

// TestChainStopsWhenFileChanged is the guard that matters most: a file
// rewritten between planning and applying must not be acted on at all.
func TestChainStopsWhenFileChanged(t *testing.T) {
	root := t.TempDir()
	src := write(t, filepath.Join(root, "x.pdf"), "planned", 0o644)
	c := chainFor(t, root, "x.pdf",
		plan.Step{Kind: plan.Move, Rule: "a", Src: src, Dst: filepath.Join(root, "W", "x.pdf")},
		plan.Step{Kind: plan.Rename, Rule: "b", Src: filepath.Join(root, "W", "x.pdf"), Dst: filepath.Join(root, "W", "y.pdf")},
	)
	write(t, src, "rewritten since the plan was made", 0o644)

	got := Chain(c)
	if got[0].Status != "failed" || !strings.Contains(got[0].Detail, "changed since plan") {
		t.Fatalf("first step = %+v; want failed \"changed since plan\"", got[0])
	}
	if got[1].Status != "skipped" {
		t.Errorf("second step = %+v; want skipped after the failure", got[1])
	}
	if b, _ := os.ReadFile(src); string(b) != "rewritten since the plan was made" {
		t.Error("the changed file was modified anyway")
	}
}

func TestChainTrashAndPermanentDelete(t *testing.T) {
	root := t.TempDir()
	t.Setenv("HOME", root)
	t.Setenv("XDG_DATA_HOME", filepath.Join(root, "share"))
	t.Setenv("XDG_STATE_HOME", "")
	t.Setenv("XDG_CONFIG_HOME", "")
	t.Setenv("XDG_CACHE_HOME", "")

	gone := write(t, filepath.Join(root, "gone.pdf"), "trash me", 0o644)
	c1 := chainFor(t, root, "gone.pdf", plan.Step{Kind: plan.Trash, Rule: "dups", Src: gone})
	r1 := Chain(c1)
	if r1[0].Status != "ok" || r1[0].Entry == "" {
		t.Fatalf("trash step = %+v; want ok with an Entry name", r1[0])
	}
	if r1[0].DisplacedEntry != "" {
		t.Errorf("DisplacedEntry = %q, want empty: a plain trash step displaces nothing", r1[0].DisplacedEntry)
	}
	if _, err := os.Stat(gone); !os.IsNotExist(err) {
		t.Error("the trashed file is still in place")
	}

	nuked := write(t, filepath.Join(root, "nuked.pdf"), "unlink me", 0o644)
	c2 := chainFor(t, root, "nuked.pdf", plan.Step{Kind: plan.DeletePermanent, Rule: "old", Src: nuked})
	if r2 := Chain(c2); r2[0].Status != "ok" {
		t.Fatalf("permanent delete = %+v", r2[0])
	}
	if _, err := os.Stat(nuked); !os.IsNotExist(err) {
		t.Error("the permanently deleted file is still in place")
	}
}

func TestChainReChecksConflictAtExecutionTime(t *testing.T) {
	root := t.TempDir()
	src := write(t, filepath.Join(root, "x.pdf"), "mine", 0o644)
	dst := filepath.Join(root, "W", "x.pdf")
	c := chainFor(t, root, "x.pdf", plan.Step{Kind: plan.Move, Rule: "a", Src: src, Dst: dst})
	// Something took the planned name between planning and applying.
	write(t, dst, "someone else got here first", 0o644)

	got := Chain(c)
	if got[0].Status != "ok" {
		t.Fatalf("step = %+v", got[0])
	}
	if got[0].Dst == dst {
		t.Error("the executor overwrote a name that appeared after planning")
	}
	if !strings.HasSuffix(got[0].Dst, "x_1.pdf") {
		t.Errorf("Dst = %q, want the next free name", got[0].Dst)
	}
	if b, _ := os.ReadFile(dst); string(b) != "someone else got here first" {
		t.Error("the file that took the planned name was overwritten")
	}
}

func TestChainSkippedStepIsNotAttempted(t *testing.T) {
	root := t.TempDir()
	src := write(t, filepath.Join(root, "x.pdf"), "content", 0o644)
	c := chainFor(t, root, "x.pdf",
		plan.Step{Kind: plan.Move, Rule: "a", Src: src, Dst: filepath.Join(root, "W", "x.pdf"), Skip: "target exists"},
	)
	if got := Chain(c); got[0].Status != "skipped" || got[0].Detail != "target exists" {
		t.Fatalf("result = %+v; want skipped carrying the planning reason", got[0])
	}
	if _, err := os.Stat(filepath.Join(root, "W")); !os.IsNotExist(err) {
		t.Error("a skipped step created its destination directory")
	}
	if _, err := os.Stat(src); err != nil {
		t.Error("a skipped step moved the file anyway")
	}
	_ = time.Now
}

// TestChainDisplacedFileRestoresFromDisplacedEntry is the fix-round-1 test:
// DisplacedEntry must be usable for undo, not merely present. It proves
// that by actually restoring the displaced file from the Trash and checking
// its content, not just that the field is non-empty. The displaced file
// sits at its own path, distinct from the step's own Dst: were the two the
// same (the ordinary overwrite shape), the mover's own file would already
// occupy that name by the time Restore ran, and Restore correctly refuses
// to land on an occupied path — this test isolates DisplacedEntry's own
// round-trip instead of also exercising that refusal.
func TestChainDisplacedFileRestoresFromDisplacedEntry(t *testing.T) {
	root := t.TempDir()
	t.Setenv("HOME", root)
	t.Setenv("XDG_DATA_HOME", filepath.Join(root, "share"))
	t.Setenv("XDG_STATE_HOME", "")
	t.Setenv("XDG_CONFIG_HOME", "")
	t.Setenv("XDG_CACHE_HOME", "")

	src := write(t, filepath.Join(root, "x.pdf"), "mine", 0o644)
	displaced := write(t, filepath.Join(root, "old", "y.pdf"), "displaced content", 0o644)
	dst := filepath.Join(root, "W", "x.pdf")

	c := chainFor(t, root, "x.pdf", plan.Step{Kind: plan.Move, Rule: "a", Src: src, Dst: dst, Displaces: displaced})

	got := Chain(c)
	if got[0].Status != "ok" {
		t.Fatalf("step = %+v", got[0])
	}
	if got[0].DisplacedEntry == "" {
		t.Fatal("DisplacedEntry is empty; undo has no way to find the displaced file")
	}
	if got[0].Entry != "" {
		t.Errorf("Entry = %q, want empty: this step is a Move, not itself a Trash step", got[0].Entry)
	}
	if _, err := os.Stat(displaced); !os.IsNotExist(err) {
		t.Error("the displaced file is still at its old path")
	}
	if b, err := os.ReadFile(dst); err != nil || string(b) != "mine" {
		t.Errorf("the move's own destination = %q, %v", b, err)
	}

	restored, err := trash.Restore(got[0].DisplacedEntry)
	if err != nil {
		t.Fatalf("Restore(%q): %v", got[0].DisplacedEntry, err)
	}
	if restored != displaced {
		t.Errorf("restored = %q, want %q", restored, displaced)
	}
	if b, err := os.ReadFile(restored); err != nil || string(b) != "displaced content" {
		t.Errorf("restored content = %q, %v; want the displaced file's own content", b, err)
	}
}

// TestChainRunsRenameStep is the fix-round-2 gap: apply_test.go's only other
// Rename (in TestChainStopsWhenFileChanged) is always reported "skipped",
// because the Move before it is made to fail on purpose, so
// "case plan.Rename: err = os.Rename(step.Src, dst)" is never exercised by
// a passing test. A reversed-argument typo there would compile, pass every
// other test, pass make ci, and surface only as live data corruption.
func TestChainRunsRenameStep(t *testing.T) {
	root := t.TempDir()
	src := write(t, filepath.Join(root, "x.pdf"), "content", 0o644)
	dst := filepath.Join(root, "y.pdf")
	c := chainFor(t, root, "x.pdf", plan.Step{Kind: plan.Rename, Rule: "a", Src: src, Dst: dst})

	got := Chain(c)
	if got[0].Status != "ok" {
		t.Fatalf("step = %+v", got[0])
	}
	if _, err := os.Stat(src); !os.IsNotExist(err) {
		t.Error("the old name still exists after a successful rename")
	}
	if b, err := os.ReadFile(dst); err != nil || string(b) != "content" {
		t.Errorf("the new name = %q, %v; want the original content at the new name", b, err)
	}
}

// TestChainMadeIsOutermostFirstForNestedDirectories is the fix-round-2 gap:
// every other test creates at most one missing directory level, so
// mkdirAllTracked's outermost-first ordering is correct by trace but
// unpinned by any assertion. Task 5 removes these directories in reverse,
// so a later accidental reordering would break undo while passing
// everything else here.
func TestChainMadeIsOutermostFirstForNestedDirectories(t *testing.T) {
	root := t.TempDir()
	write(t, filepath.Join(root, "x.pdf"), "content", 0o644)
	dst := filepath.Join(root, "A", "B", "x.pdf")
	c := chainFor(t, root, "x.pdf", plan.Step{Kind: plan.Copy, Rule: "a", Src: filepath.Join(root, "x.pdf"), Dst: dst})

	got := Chain(c)
	if got[0].Status != "ok" {
		t.Fatalf("step = %+v", got[0])
	}
	want := []string{filepath.Join(root, "A"), filepath.Join(root, "A", "B")}
	if !slices.Equal(got[0].Made, want) {
		t.Errorf("Made = %v, want %v (outermost first)", got[0].Made, want)
	}
}

// TestMoveFileRefusesOccupiedDestination is item 16 (fix round 2026-09-12,
// plan 5 Task 2): moveFile must refuse an occupied destination on its own,
// not merely rely on runFileStep having already checked - the exact
// arrangement that produced plan 4's Task 5 Critical, where a helper that
// replaced silently was trusted because some caller had checked. Called
// directly, bypassing runFileStep's own pre-check entirely.
func TestMoveFileRefusesOccupiedDestination(t *testing.T) {
	dir := t.TempDir()
	src := write(t, filepath.Join(dir, "x.pdf"), "source", 0o644)
	dst := write(t, filepath.Join(dir, "y.pdf"), "already there", 0o644)

	if err := moveFile(src, dst); err == nil {
		t.Fatal("moveFile overwrote an existing destination")
	}
	if b, err := os.ReadFile(src); err != nil || string(b) != "source" {
		t.Errorf("moveFile touched its source: %q, %v", b, err)
	}
	if b, err := os.ReadFile(dst); err != nil || string(b) != "already there" {
		t.Errorf("moveFile touched its destination: %q, %v", b, err)
	}
}

// TestRenameFileRefusesOccupiedDestination is item 16's other half:
// runFileStep's bare os.Rename call for the Rename kind was just as
// unguarded in itself as moveFile was. renameFile is the helper that now
// carries the same independent guard, called directly here.
func TestRenameFileRefusesOccupiedDestination(t *testing.T) {
	dir := t.TempDir()
	src := write(t, filepath.Join(dir, "x.pdf"), "source", 0o644)
	dst := write(t, filepath.Join(dir, "y.pdf"), "already there", 0o644)

	if err := renameFile(src, dst); err == nil {
		t.Fatal("renameFile overwrote an existing destination")
	}
	if b, err := os.ReadFile(src); err != nil || string(b) != "source" {
		t.Errorf("renameFile touched its source: %q, %v", b, err)
	}
	if b, err := os.ReadFile(dst); err != nil || string(b) != "already there" {
		t.Errorf("renameFile touched its destination: %q, %v", b, err)
	}
}