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

package engine

import (
	"context"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"testing"
	"time"

	"krino/internal/journal"
	"krino/internal/plan"
	"krino/internal/trash"
)

// appliedRun makes each directory of files under the sandbox home (a map of
// directory name to file name to content, every file two hours old), writes
// rules for each, and applies every chain of every directory in one run. It
// returns the engine, the run id, the home directory and the log path.
func appliedRun(t *testing.T, files map[string]map[string]string, rules map[string]string) (*Engine, string, string, string) {
	t.Helper()
	h := sandbox(t)
	old := time.Now().Add(-2 * time.Hour)
	var names []string
	for dir, fs := range files {
		names = append(names, dir)
		for name, body := range fs {
			p := filepath.Join(h, dir, name)
			if err := os.MkdirAll(filepath.Dir(p), 0o755); err != nil {
				t.Fatal(err)
			}
			if err := os.WriteFile(p, []byte(body), 0o644); err != nil {
				t.Fatal(err)
			}
			if err := os.Chtimes(p, old, old); err != nil {
				t.Fatal(err)
			}
		}
	}
	sort.Strings(names)
	main := writeConfig(t, h, `(include "`+strings.Join(names, `" "`)+`")`, rules)
	e, errs := Load(main)
	if len(errs) > 0 {
		t.Fatal(errs)
	}
	logPath := filepath.Join(h, ".local", "state", "krino", "krino.log")
	j, err := journal.Open(logPath)
	if err != nil {
		t.Fatal(err)
	}
	defer j.Close()
	run := journal.NewRunID(time.Now())
	claims := plan.NewClaims()
	for _, d := range e.Dirs {
		dp, err := e.Plan(context.Background(), d, claims)
		if err != nil {
			t.Fatal(err)
		}
		approved := map[string]bool{}
		for _, c := range dp.Chains {
			approved[c.File.Rel] = true
		}
		res, err := e.Apply(context.Background(), dp, approved, j, run)
		if err != nil || res.Failed != 0 {
			t.Fatalf("apply %s: %v, %+v", d.Name, err, res)
		}
	}
	return e, run, h, logPath
}

// undoFileNamed returns the plan's file for dir and name, failing the test
// when there is none.
func undoFileNamed(t *testing.T, up *UndoPlan, dir, name string) UndoFile {
	t.Helper()
	for _, f := range up.Files {
		if f.Dir == dir && f.File == name {
			return f
		}
	}
	t.Fatalf("no %s/%s in the undo plan: %+v", dir, name, up.Files)
	return UndoFile{}
}

// TestUndoRefusesAReusedTrashEntry: the Trash is emptied and another file of
// the same name trashed after the run; undo must not restore that file in
// place of the one the run trashed (review M2).
func TestUndoRefusesAReusedTrashEntry(t *testing.T) {
	e, run, h, _ := appliedRun(t, map[string]map[string]string{"dl": {"a.pdf": "one"}},
		map[string]string{"dl": "(path \"~/dl\")\n(rule \"r\" (rename \"r-{name}\") (delete))\n"})
	if err := os.RemoveAll(trash.Dir()); err != nil {
		t.Fatal(err)
	}
	other := filepath.Join(h, "Documents", "r-a.pdf")
	if err := os.MkdirAll(filepath.Dir(other), 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(other, []byte("an unrelated document"), 0o644); err != nil {
		t.Fatal(err)
	}
	if entry, err := trash.Put(other); err != nil || entry != "r-a.pdf" {
		t.Fatalf("trash.Put = %q, %v", entry, err)
	}
	up, err := e.PlanUndo(run)
	if err != nil {
		t.Fatal(err)
	}
	if f := undoFileNamed(t, up, "dl", "a.pdf"); !strings.Contains(f.Refused, "trash entry") {
		t.Errorf("Refused = %q; want a refusal naming the trash entry", f.Refused)
	}
}

// TestUndoRefusesATrashEntryThatChanged: a trash entry that is no longer the
// file the run put there (its size changed) is refused, like a moved file
// that changed (review M2).
func TestUndoRefusesATrashEntryThatChanged(t *testing.T) {
	e, run, _, _ := appliedRun(t, map[string]map[string]string{"dl": {"a.pdf": "one"}},
		map[string]string{"dl": "(path \"~/dl\")\n(rule \"r\" (delete))\n"})
	if err := os.WriteFile(filepath.Join(trash.Dir(), "files", "a.pdf"), []byte("a longer, different body"), 0o644); err != nil {
		t.Fatal(err)
	}
	up, err := e.PlanUndo(run)
	if err != nil {
		t.Fatal(err)
	}
	if f := undoFileNamed(t, up, "dl", "a.pdf"); f.Refused == "" {
		t.Error("a changed trash entry was not refused")
	}
}

// TestUndoKeepsSameNamedFilesOfTwoDirectoriesApart: a.pdf from dl and
// a.pdf from scans, moved in one run, are two files to undo, each refused or
// restored on its own (review M7).
func TestUndoKeepsSameNamedFilesOfTwoDirectoriesApart(t *testing.T) {
	e, run, h, logPath := appliedRun(t,
		map[string]map[string]string{"dl": {"a.pdf": "from dl"}, "scans": {"a.pdf": "from scans"}},
		map[string]string{
			"dl":    "(path \"~/dl\")\n(rule \"r\" (move \"~/Archive\"))\n",
			"scans": "(path \"~/scans\")\n(rule \"r\" (move \"~/Archive\"))\n",
		})
	up, err := e.PlanUndo(run)
	if err != nil {
		t.Fatal(err)
	}
	if len(up.Files) != 2 {
		t.Fatalf("undo plan has %d files, want 2: %+v", len(up.Files), up.Files)
	}
	scansCopy := undoFileNamed(t, up, "scans", "a.pdf").Steps[0].Src
	if err := os.WriteFile(scansCopy, []byte("from scans, edited since"), 0o644); err != nil {
		t.Fatal(err)
	}
	up, err = e.PlanUndo(run)
	if err != nil {
		t.Fatal(err)
	}
	if undoFileNamed(t, up, "scans", "a.pdf").Refused == "" || undoFileNamed(t, up, "dl", "a.pdf").Refused != "" {
		t.Fatalf("want only the edited scans file refused: %+v", up.Files)
	}
	j, err := journal.Open(logPath)
	if err != nil {
		t.Fatal(err)
	}
	defer j.Close()
	if _, err := e.ApplyUndo(context.Background(), up, j, journal.NewRunID(time.Now())); err != nil {
		t.Fatal(err)
	}
	if b, err := os.ReadFile(filepath.Join(h, "dl", "a.pdf")); err != nil || string(b) != "from dl" {
		t.Errorf("dl/a.pdf after undo: %q, %v", b, err)
	}
}

// TestUndoRechecksAtExecution: a file edited after the undo was planned (for
// example while its review was open) is not moved back (review undo F8).
func TestUndoRechecksAtExecution(t *testing.T) {
	e, run, h, logPath := appliedRun(t, map[string]map[string]string{"dl": {"a.pdf": "one"}},
		map[string]string{"dl": "(path \"~/dl\")\n(rule \"r\" (move \"Out\"))\n"})
	up, err := e.PlanUndo(run)
	if err != nil {
		t.Fatal(err)
	}
	moved := filepath.Join(h, "dl", "Out", "a.pdf")
	if err := os.WriteFile(moved, []byte("edited during review"), 0o644); err != nil {
		t.Fatal(err)
	}
	j, err := journal.Open(logPath)
	if err != nil {
		t.Fatal(err)
	}
	defer j.Close()
	res, err := e.ApplyUndo(context.Background(), up, j, journal.NewRunID(time.Now()))
	if err != nil {
		t.Fatal(err)
	}
	if res.Failed != 1 {
		t.Errorf("Failed = %d, want 1", res.Failed)
	}
	if b, _ := os.ReadFile(moved); string(b) != "edited during review" {
		t.Errorf("the edited file was moved or changed: %q", b)
	}
}

// TestUndoLeavesNoDirectoriesBehind: undo passing a file back through a
// directory it had already removed for another file recreates it; that
// directory must be gone again when the undo ends (review undo F6).
func TestUndoLeavesNoDirectoriesBehind(t *testing.T) {
	e, run, h, logPath := appliedRun(t, map[string]map[string]string{"dl": {"a.pdf": "one", "b.pdf": "two"}},
		map[string]string{"dl": "(path \"~/dl\")\n(rule \"r\" (move \"Out/{mtime:%Y}\") (move \"Out\"))\n"})
	up, err := e.PlanUndo(run)
	if err != nil {
		t.Fatal(err)
	}
	j, err := journal.Open(logPath)
	if err != nil {
		t.Fatal(err)
	}
	defer j.Close()
	if res, err := e.ApplyUndo(context.Background(), up, j, journal.NewRunID(time.Now())); err != nil || res.Failed != 0 {
		t.Fatalf("undo: %v, %+v", err, res)
	}
	if _, err := os.Stat(filepath.Join(h, "dl", "Out")); !os.IsNotExist(err) {
		t.Errorf("dl/Out is left behind: %v", err)
	}
}

// TestUndoCanBeFinishedAfterAFailure: an undo whose last reversal failed
// (something took the original name) leaves the file part way back; once
// the obstacle is gone, undoing the same run again offers only the step
// that is left, and finishes it (review M10).
func TestUndoCanBeFinishedAfterAFailure(t *testing.T) {
	e, run, h, logPath := appliedRun(t, map[string]map[string]string{"dl": {"a.pdf": "one"}},
		map[string]string{"dl": "(path \"~/dl\")\n(rule \"r\" (rename \"r-{name}\") (move \"Out\"))\n"})
	up, err := e.PlanUndo(run)
	if err != nil {
		t.Fatal(err)
	}
	blocker := filepath.Join(h, "dl", "a.pdf")
	if err := os.WriteFile(blocker, []byte("in the way"), 0o644); err != nil {
		t.Fatal(err)
	}
	undo := func(up *UndoPlan) *ApplyResult {
		t.Helper()
		j, err := journal.Open(logPath)
		if err != nil {
			t.Fatal(err)
		}
		defer j.Close()
		res, err := e.ApplyUndo(context.Background(), up, j, journal.NewRunID(time.Now()))
		if err != nil {
			t.Fatal(err)
		}
		return res
	}
	if res := undo(up); res.Failed != 1 {
		t.Fatalf("first undo: Failed = %d, want 1 (the rename back is blocked)", res.Failed)
	}
	if err := os.Remove(blocker); err != nil {
		t.Fatal(err)
	}
	time.Sleep(10 * time.Millisecond) // a new run id
	again, err := e.PlanUndo(run)
	if err != nil {
		t.Fatal(err)
	}
	f := undoFileNamed(t, again, "dl", "a.pdf")
	if f.Refused != "" || len(f.Steps) != 1 || f.Steps[0].Action != "undo-rename" {
		t.Fatalf("second plan: %+v; want one undo-rename step", f)
	}
	if res := undo(again); res.Failed != 0 || res.Applied != 1 {
		t.Fatalf("second undo: %+v", res)
	}
	if b, err := os.ReadFile(filepath.Join(h, "dl", "a.pdf")); err != nil || string(b) != "one" {
		t.Errorf("dl/a.pdf = %q, %v; want the original back", b, err)
	}
}

// TestApplyReportsAStepThatCouldNotBeLogged: when the log stops accepting
// writes mid-chain, the step that already ran is named in the error - file,
// action and where the file is now - so the user can find what undo cannot
// see (re-review N1).
func TestApplyReportsAStepThatCouldNotBeLogged(t *testing.T) {
	h := sandbox(t)
	p := filepath.Join(h, "dl", "a.pdf")
	os.MkdirAll(filepath.Dir(p), 0o755)
	os.WriteFile(p, []byte("one"), 0o644)
	old := time.Now().Add(-2 * time.Hour)
	os.Chtimes(p, old, old)
	main := writeConfig(t, h, `(include "dl")`, map[string]string{"dl": "(path \"~/dl\")\n(rule \"r\" (rename \"r-{name}\") (move \"Out\"))\n"})
	e, errs := Load(main)
	if len(errs) > 0 {
		t.Fatal(errs)
	}
	dp, err := e.Plan(context.Background(), e.Dirs[0], plan.NewClaims())
	if err != nil {
		t.Fatal(err)
	}
	j, err := journal.Open(filepath.Join(h, "state", "krino.log"))
	if err != nil {
		t.Fatal(err)
	}
	calls := 0
	e.Now = func() time.Time {
		calls++
		if calls == 3 { // run-start and the rename are logged; the move is not
			j.Close()
		}
		return time.Now()
	}
	_, err = e.Apply(context.Background(), dp, map[string]bool{"a.pdf": true}, j, "R")
	if err == nil {
		t.Fatal("apply succeeded with a closed log")
	}
	for _, want := range []string{"a.pdf", "move", "could not be logged", "Out/r-a.pdf"} {
		if !strings.Contains(err.Error(), want) {
			t.Errorf("error %q does not mention %q", err, want)
		}
	}
}

// TestUndoRefusesOnlyTheFileWithADamagedLine: a crash that cuts one file's
// log line refuses that file; the other files of the run are still undone
// (re-review N1).
func TestUndoRefusesOnlyTheFileWithADamagedLine(t *testing.T) {
	e, run, h, logPath := appliedRun(t, map[string]map[string]string{"dl": {"a.pdf": "one", "b.pdf": "two"}},
		map[string]string{"dl": "(path \"~/dl\")\n(rule \"r\" (move \"Out\"))\n"})
	raw, err := os.ReadFile(logPath)
	if err != nil {
		t.Fatal(err)
	}
	lines := strings.Split(strings.TrimRight(string(raw), "\n"), "\n")
	for i, l := range lines {
		if strings.Contains(l, "\tb.pdf\t") && strings.Contains(l, "\tmove\t") {
			lines[i] = l[:len(l)/2] // cut mid-write
		}
	}
	if err := os.WriteFile(logPath, []byte(strings.Join(lines, "\n")+"\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	up, err := e.PlanUndo(run)
	if err != nil {
		t.Fatalf("PlanUndo refused the whole run: %v", err)
	}
	if f := undoFileNamed(t, up, "dl", "b.pdf"); !strings.Contains(f.Refused, "damaged") {
		t.Errorf("b.pdf: Refused %q; want its damaged log named", f.Refused)
	}
	if f := undoFileNamed(t, up, "dl", "a.pdf"); f.Refused != "" {
		t.Errorf("a.pdf refused: %q", f.Refused)
	}
	j, err := journal.Open(logPath)
	if err != nil {
		t.Fatal(err)
	}
	defer j.Close()
	if _, err := e.ApplyUndo(context.Background(), up, j, journal.NewRunID(time.Now())); err != nil {
		t.Fatal(err)
	}
	if b, err := os.ReadFile(filepath.Join(h, "dl", "a.pdf")); err != nil || string(b) != "one" {
		t.Errorf("a.pdf not restored: %q %v", b, err)
	}
}