Editing tracklists

applyEdits(text, edits) (apply_edits in Python) takes a tracklist as text and returns new text. It's built for editors: you get back the lines it changed, and every other line keeps its bytes and its line ending.

JavaScript

import { applyEdits, parseTracklist } from "trackparse/tracklist";

Python

from trackparse.tracklist import apply_edits, parse_tracklist

Using the list from the previous page, apply the suggested fix, then push everything from line 5 on back by 45 seconds:

JavaScript

const fix = parseTracklist(text).warnings[1].suggestion;   // { line: 8, raw: '01:11:02', seconds: 4262 }

const result = applyEdits(text, [
  { op: "set-time", line: fix.line, seconds: fix.seconds },
  { op: "shift", seconds: 45, from: 5 },
]);

result.changed;   // [ 5, 6, 7, 8, 9 ]
result.warnings;  // [ { code: 'style-upgraded', edit: 1, line: 5 } ]
result.text.split("\r\n").slice(4);
// [
//   '01:00:16 Alix Perez - Fade Away',
//   '01:03:55 Interview with Hybris',
//   '01:08:29 Imanu - Sacrifice',
//   '01:11:47 Current Value feat. Teddy Killerz - Payload',
//   '01:16:21 Hybris - Spinning Top'
// ]

Python

fix = parse_tracklist(text).warnings[1].suggestion   # Suggestion(line=8, raw='01:11:02', seconds=4262)

result = apply_edits(text, [
    {"op": "set-time", "line": fix.line, "seconds": fix.seconds},
    {"op": "shift", "seconds": 45, "from": 5},
])

result.changed   # (5, 6, 7, 8, 9)
result.warnings  # (EditWarning(code='style-upgraded', edit=1, line=5),)
result.text.split("\r\n")[4:]
# ['01:00:16 Alix Perez - Fade Away',
#  '01:03:55 Interview with Hybris',
#  '01:08:29 Imanu - Sacrifice',
#  '01:11:47 Current Value feat. Teddy Killerz - Payload',
#  '01:16:21 Hybris - Spinning Top']

In Python the edits are plain dicts with the same keys, "from" included.

Lines 1 to 4 are untouched, CRLF included. Edits run in order, each on the text the previous one produced, with line numbers as that text has them.

The edits

Edit	Effect
{ op: "set-time", line, seconds }	Rewrite the time on that line
{ op: "shift", seconds, lines?, from? }	Add seconds (negative to go back) to the listed lines, to every timed line from from on, or to all of them
{ op: "sort-by-time" }	Reorder by time. Untimed lines move with the timed line above them, and lines before the first time stay on top
{ op: "set-rest", line, rest }	Replace everything after the time, for example with format(track) (format_track)
{ op: "insert", after, text }	Insert a line after line after (0 puts it at the top). It gets the text's usual line ending
{ op: "delete", line }	Remove a line

Times keep their style

A rewritten time looks like its neighbours. Hours or no hours, digit widths and fraction digits are all kept, so 52:47 plus 45 seconds is 53:32, not 00:53:32.

When a time without hours crosses the hour, it gains hours in the style the rest of the list uses (59:31 → 01:00:16, or 1:00:16 if the list writes one-digit hours). The edit reports style-upgraded so you know the line got longer.

When an edit can't apply

Edits never throw. A bad one changes nothing and reports why:

Code	When
edit-invalid	missing line, no time on the line, NaN or infinity, a time too large to write, a line break inside text or rest, an unknown op
time-clamped	the time would go below zero, so it was set to zero
style-upgraded	a time gained hours (see above)

Each edit warning is { code, edit, line }, where edit is the index in your edits array and line is null when the edit doesn't name a line.

Guarantees

The property tests check these on random text and random edit lists:

• applyEdits(t, []) returns t.
• An edit never touches a line it doesn't name.
• shift(+s) followed by shift(-s) gives back the original text, unless something was clamped or upgraded on the way.