plan 9: an interrupted or failed undo can be finished

1 files changed, 37 insertions, 0 deletions

diff --git a/internal/journal/read.go b/internal/journal/read.go
index 3de15d2..de06422 100644
--- a/internal/journal/read.go
+++ b/internal/journal/read.go
@@ -43,6 +43,42 @@ type Run struct {
 	Dirs   []string
 	Counts map[string]int // action -> count of status "ok"
 	Undone bool           // a later run reversed this one
+	UndoOf string         // for an undo run, the run it reverses; "" otherwise
+}
+
+// ReversedKey identifies one reversal an undo run carried out: the file's
+// directory and name, the undo action and the path it started from - enough
+// to tell which step of the original run it reversed.
+type ReversedKey struct {
+	Dir, File, Action, Src string
+}
+
+// ReversedSteps counts, for runID, every reversal that earlier undo runs of
+// it completed ("ok" undo- entries of runs whose run-start says they undo
+// runID), so a later undo of the same run can offer only what is left
+// (review M10). An undo run's own unparsable lines are skipped; a missing
+// reversal is then offered again, where its own checks refuse it if it had
+// in fact happened.
+func ReversedSteps(path, runID string) (map[ReversedKey]int, error) {
+	lines, err := readLines(path)
+	if err != nil {
+		return nil, err
+	}
+	undoRuns := map[string]bool{}
+	for _, line := range lines {
+		if e, ok := parseLine(line); ok && e.Action == "run-start" && e.Detail == UndoOf(runID) {
+			undoRuns[e.Run] = true
+		}
+	}
+	out := map[ReversedKey]int{}
+	for _, line := range lines {
+		e, ok := parseLine(line)
+		if !ok || !undoRuns[e.Run] || e.Status != "ok" || !strings.HasPrefix(e.Action, "undo-") {
+			continue
+		}
+		out[ReversedKey{Dir: e.Dir, File: e.File, Action: e.Action, Src: e.Src}]++
+	}
+	return out, nil
 }
 
 // Entries returns every entry belonging to runID, in file order. A line
@@ -198,6 +234,7 @@ func Runs(path string, n int) ([]Run, error) {
 	sort.SliceStable(runs, func(i, j int) bool { return runs[i].Start.After(runs[j].Start) })
 	for i := range runs {
 		runs[i].Undone = undoes[runs[i].ID]
+		runs[i].UndoOf = pendingUndo[runs[i].ID]
 	}
 
 	if n > 0 && n < len(runs) {