From 62cf77b09298f31d2bc9d6b1e25e011e19fede5a Mon Sep 17 00:00:00 2001
From: Thomas Voss <mail@thomasvoss.com>
Date: Thu, 24 Jul 2025 20:47:07 +0200
Subject: Rename docs/ to doc/

---
 doc/i18n.md | 131 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 131 insertions(+)
 create mode 100644 doc/i18n.md

(limited to 'doc/i18n.md')

diff --git a/doc/i18n.md b/doc/i18n.md
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--- /dev/null
+++ b/doc/i18n.md
@@ -0,0 +1,131 @@
+# The Internationalization System
+
+## Extracting Translations
+
+For translators to be able to translate text, and for us to be able to
+work with those translations, we need translation files.  These files are
+located in the `/po` directory.  These files are automatically generated
+by running the `make po` command.  In order to extract translations from
+the source code, the `make po` command will search for calls to the
+`Get()` family of functions, such as `Get()` and `GetN()`.
+
+```go
+func example(n int) {
+	/* Not extracted for translation */
+	fmt.Println("Hello, Sailor!")
+
+	/* Extracted for translation */
+	fmt.Println(i18n.GetN("1 book", "{N} books", n,
+		map[string]any{"N": n}))
+}
+```
+
+Sometimes you want to provide additional context about a translation to
+the translators.  You can do this by placing a comment above the
+translated string with the prefix ‘TRANSLATORS:’.
+
+```go
+func example() string {
+	/* TRANSLATORS: ‘Home’ button on the navigation bar */
+	return i18n.Get("Home")
+}
+```
+
+Especially when working in HTML templates, you may have a string that you
+want to go through the formatting system but _not_ be marked for
+translation.  You can do this by calling the underlying `Sprintf()`
+function instead.
+
+```html
+<p>{{ .Printer.Sprintf "{N:m}" (map "N" 2) }}</p>
+```
+
+## The Formatting System
+
+For string formatting we use a custom implementation of `Sprintf()`, and
+all `Get*()` functions format the translated strings using our own
+`Sprintf()`.
+
+Do note that all `Sprintf()` output is automatically HTML escaped.
+
+Unlike the standard `Sprintf()`, we use named placeholders enclosed by
+curly braces instead of percent codes.  As placeholders are named, they
+need to be passed via a map of type `map[string]any`.
+
+```go
+func example() {
+	status := "late"
+
+	/* Go’s Sprintf */
+	_ = fmt.Sprintf("The bus is %s", status)
+
+	/* Our Sprintf */
+	_ = i18n.Sprintf("The bus is {LateOrEarly}",
+		map[string]any{"LateOrEarly": status})
+}
+```
+
+The result is a lot more visually-noisy than what Go does — mostly due
+to the map syntax — but it offers infinitely more information to
+translators, which is important.
+
+Translation functions can be provided multiple argument maps, and maps
+can be easily created in HTML templates using the `map` function.
+
+```html
+{{ $nlargs := (map "DutchStart" `<span lang="nl"><em>`
+                   "DutchEnd"   `em,span`) }}
+<p>{{ .Get "{Name} said ‘{DutchStart:r}{Quote}{DutchEnd:E}’!"
+      (map "Name" "Thomas" "Quote" "...") $nlargs }}</p>
+```
+
+In a placeholder you can also use a colon and additional character code
+to customize how formatting is performed.  The default behaviour is as
+follows:
+
+- Strings are printed verbatim
+- Numbers (`int`) and floats (`float64`) are formatted with the
+  locale-specific grouping- and decimal separators
+- Dates (`time.Time`) are formatted according to the current locale
+- Other types are coerced to a string by `fmt.Sprintf()` and then printed
+  verbatim
+
+The following character codes are available with the following behaviour:
+
+| Code | Mnemonic           | Description                                                 |
+| ---- | ------------------ | ----------------------------------------------------------- |
+| `e`  | \[e]mail           | inserts a link to an email address                          |
+| `E`  | \[E]nd             | inserts closing-tags for the comma-separated HTML tags      |
+| `l`  | \[l]ink (internal) | links to an internal page                                   |
+| `L`  | \[L]ink (external) | links to an external page                                   |
+| `m`  | \[m]onetary        | formats the given `int` or `float64` as an amount of Euros. |
+| `r`  | \[r]aw             | inserts the given string verbatim without HTML escaping     |
+
+```html
+<!-- <a href="mailto:help@euro-cash.eu">help@euro-cash.eu</a> -->
+<p>{{ .Get "{Email:e}" (map "Email" "help@euro-cash.eu") }}</p>
+
+<!-- <span lang="sv"><em>Växjösjön</em></span> -->
+<p>{{ .Get "{SwedishStart:r}Växjösjön{SwedishEnd:E}"
+      (map "SwedishStart" `<span lang="sv"><em>`
+           "SwedishEnd"   "em,span") }}</p>
+
+<!-- Click <a href="/banknotes">here</a>! -->
+<p>{{ .Get "Click {Link:l}here{-:E}!"
+      (map "Link" "/banknotes") }}</p>
+
+<!-- Click <a href="https://euro-cash.eu" target="_blank">here</a>! -->
+<p>{{ .Get "Click {Link:L}here{-:E}!"
+      (map "Link" "https://euro-cash.eu") }}</p>
+
+<!-- Varies per locale -->
+<!-- €1 and €1.00 -->
+<p>{{ .Get "{1:m} and {1.00:m}" (map "1" 1 "1.00" 1.00) }}</p>
+```
+
+Some additional notes:
+- The `-` name is special. `{-:E}` inserts `</a>`.  This exists because
+  of how often you need to do this.
+- The `m` character code won’t include decimals when the argument is an
+  integer, and will include the decimals when the argument is a
+  floating-point number.
\ No newline at end of file
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