Fixes #151.

- Simplify and improve datetime, date, and time parsing
- Add support for backfillTimezones and inferTimezoneFromDatestamps
- Add tests

.vscode/settings.json

@@ -1,7 +1,10 @@
 {
   "typescript.tsdk": "./node_modules/typescript/lib",
   "cSpell.words": [
+    "creat",
+    "Degrouped",
     "exiftool's",
+    "modif",
     "noexif"
   ],
   "cSpell.ignoreWords": [

src/DateTime.ts

@@ -41,3 +41,12 @@ export function toExifString(d: DateOrTime): Maybe<string> {
     return d?.toExifString?.()
   }
 }
+
+export function hms(
+  d: DateTime,
+  opts?: { includeMilliseconds?: boolean }
+): string {
+  return d.toFormat(
+    "HH:mm:ss" + (opts?.includeMilliseconds === true ? ".SSS" : "")
+  )
+}

src/DefaultExifToolOptions.ts

@@ -45,6 +45,8 @@ export const DefaultExifToolOptions: Omit<
   ],
   includeImageDataMD5: false,
   defaultVideosToUTC: true,
+  backfillTimezones: false, // to retain prior behavior
+  inferTimezoneFromDatestamps: false, // to retain prior behavior
   geoTz: geoTz,
   isIgnorableError: isIgnorableWarning,
 })

src/ExifDate.ts

@@ -8,6 +8,14 @@ import { blank, pad2, toS } from "./String"
  * Encodes an ExifDate
  */
 export class ExifDate {
+  static from(exifOrIso: string): Maybe<ExifDate> {
+    return (
+      // in order of strictness:
+      this.fromExifStrict(exifOrIso) ??
+      this.fromISO(exifOrIso) ??
+      this.fromExifLoose(exifOrIso)
+    )
+  }
   static fromISO(text: string): Maybe<ExifDate> {
     return this.fromDateTime(DateTime.fromISO(text), text)
   }

src/ExifDateTime.ts

@@ -6,7 +6,7 @@ import {
   Zone,
   ZoneOptions,
 } from "luxon"
-import { dateTimeToExif } from "./DateTime"
+import { MinuteMs, dateTimeToExif } from "./DateTime"
 import { Maybe, denull } from "./Maybe"
 import { omit } from "./Object"
 import { blank, notBlank, toS } from "./String"
@@ -29,6 +29,18 @@ const TimeFmts = [
 export class ExifDateTime {
   #dt?: DateTime
 
+  static from(
+    exifOrIso: string,
+    defaultZone?: Maybe<string>
+  ): Maybe<ExifDateTime> {
+    return (
+      // in order of strictness:
+      this.fromExifStrict(exifOrIso, defaultZone) ??
+      this.fromISO(exifOrIso, defaultZone) ??
+      this.fromExifLoose(exifOrIso, defaultZone)
+    )
+  }
+
   static fromISO(
     iso: string,
     defaultZone?: Maybe<string>
@@ -381,6 +393,33 @@ export class ExifDateTime {
     )
   }
 
+  maybeMatchZone(
+    target: ExifDateTime,
+    maxDeltaMs = 14 * MinuteMs
+  ): Maybe<ExifDateTime> {
+    if (!target.hasZone) return
+    return (
+      this.setZone(target.zone, { keepLocalTime: false })?.ifClose(
+        target,
+        maxDeltaMs
+      ) ??
+      this.setZone(target.zone, { keepLocalTime: true })?.ifClose(
+        target,
+        maxDeltaMs
+      ) ??
+      this.setZone("UTC", { keepLocalTime: true })?.ifClose(target, maxDeltaMs)
+    )
+  }
+
+  private ifClose(
+    target: ExifDateTime,
+    maxDeltaMs = 14 * MinuteMs
+  ): Maybe<ExifDateTime> {
+    const ts = this.toMillis()
+    const targetTs = target.toMillis()
+    return Math.abs(ts - targetTs) <= maxDeltaMs ? this : undefined
+  }
+
   plus(duration: DurationLike) {
     let dt = this.toDateTime().plus(duration)
     if (!this.hasZone) {

src/ExifToolOptions.ts

@@ -114,10 +114,31 @@ export interface ExifToolOptions
    * Video file dates are assumed to be in UTC, rather than using timezone
    * inference used in images. To disable this default, set this to false.
    *
-   * @see <https://github.com/photostructure/exiftool-vendored.js/issues/113>
+   * @see https://github.com/photostructure/exiftool-vendored.js/issues/113
    */
   defaultVideosToUTC: boolean
 
+  /**
+   * Should we try to backfill timezones for date-times that don't have them?
+   * If set to `true`, and `defaultVideosToUTC` is also `true`, we'll try
+   * backfilling timezones for date-times that are UTC, as well.
+   *
+   * This defaults to false to retain prior versions' behavior.
+   */
+  backfillTimezones: boolean
+
+  /**
+   * We always look at TimeZone, OffsetTime, TimeZoneOffset, and GPS metadata
+   * to infer the timezone.
+   *
+   * If these strategies fail, can we infer a timezone from any non-UTC
+   * datestamp whose tag starts with "Creat" and includes an offset? (This
+   * means CreateDateSubSec, CreateDate, and CreationDate will be considered).
+   *
+   * This defaults to false to retain prior versions' behavior.
+   */
+  inferTimezoneFromDatestamps: boolean
+
   /**
    * `ExifTool` has a shebang line that assumes a valid `perl` is installed at
    * `/usr/bin/perl`.