move genStrings into its own file

1 files changed, 207 insertions, 0 deletions

diff --git a/src/util/strings.js b/src/util/strings.js
new file mode 100644
index 00000000..cf4d88c4
--- /dev/null
+++ b/src/util/strings.js
@@ -0,0 +1,207 @@
+import { logWarn } from './cli.js';
+
+// Localiz8tion time! Or l10n as the neeeeeeeerds call it. Which is a terri8le
+// name and not one I intend on using, thank you very much. (Don't even get me
+// started on """"a11y"""".)
+//
+// All the default strings are in strings-default.json, if you're curious what
+// those actually look like. Pretty much it's "I like {ANIMAL}" for example.
+// For each language, the o8ject gets turned into a single function of form
+// f(key, {args}). It searches for a key in the o8ject and uses the string it
+// finds (or the one in strings-default.json) as a templ8 evaluated with the
+// arguments passed. (This function gets treated as an o8ject too; it gets
+// the language code attached.)
+//
+// The function's also responsi8le for getting rid of dangerous characters
+// (quotes and angle tags), though only within the templ8te (not the args),
+// and it converts the keys of the arguments o8ject from camelCase to
+// CONSTANT_CASE too.
+//
+// This function also takes an optional "bindUtilities" argument; it should
+// look like a dictionary each value of which is itself a util dictionary,
+// each value of which is a function in the format (value, opts) => (...).
+// Each of those util dictionaries will 8e attached to the final returned
+// strings() function, containing functions which automatically have that
+// same strings() function provided as part of its opts argument (alongside
+// any additional arguments passed).
+//
+// Basically, it's so that instead of doing:
+//
+//     count.tracks(album.tracks.length, {strings})
+//
+// ...you can just do:
+//
+//     strings.count.tracks(album.tracks.length)
+//
+// Definitely note bindUtilities expects an OBJECT, not an array, otherwise
+// it won't 8e a8le to know what keys to attach the utilities 8y!
+//
+// Oh also it'll need access to the he.encode() function, and callers have to
+// provide that themselves, 'cuz otherwise we can't reference this file from
+// client-side code.
+export function genStrings(stringsJSON, {
+    he,
+    defaultJSON = null,
+    bindUtilities = []
+}) {
+    // genStrings will only 8e called once for each language, and it happens
+    // right at the start of the program (or at least 8efore 8uilding pages).
+    // So, now's a good time to valid8te the strings and let any warnings be
+    // known.
+
+    // May8e contrary to the argument name, the arguments should 8e o8jects,
+    // not actual JSON-formatted strings!
+    if (typeof stringsJSON !== 'object' || stringsJSON.constructor !== Object) {
+        return {error: `Expected an object (parsed JSON) for stringsJSON.`};
+    }
+    if (typeof defaultJSON !== 'object') { // typeof null === object. I h8 JS.
+        return {error: `Expected an object (parsed JSON) or null for defaultJSON.`};
+    }
+
+    // All languages require a language code.
+    const code = stringsJSON['meta.languageCode'];
+    if (!code) {
+        return {error: `Missing language code.`};
+    }
+    if (typeof code !== 'string') {
+        return {error: `Expected language code to be a string.`};
+    }
+
+    // Every value on the provided o8ject should be a string.
+    // (This is lazy, but we only 8other checking this on stringsJSON, on the
+    // assumption that defaultJSON was passed through this function too, and so
+    // has already been valid8ted.)
+    {
+        let err = false;
+        for (const [ key, value ] of Object.entries(stringsJSON)) {
+            if (typeof value !== 'string') {
+                logError`(${code}) The value for ${key} should be a string.`;
+                err = true;
+            }
+        }
+        if (err) {
+            return {error: `Expected all values to be a string.`};
+        }
+    }
+
+    // Checking is generally done against the default JSON, so we'll skip out
+    // if that isn't provided (which should only 8e the case when it itself is
+    // 8eing processed as the first loaded language).
+    if (defaultJSON) {
+        // Warn for keys that are missing or unexpected.
+        const expectedKeys = Object.keys(defaultJSON);
+        const presentKeys = Object.keys(stringsJSON);
+        for (const key of presentKeys) {
+            if (!expectedKeys.includes(key)) {
+                logWarn`(${code}) Unexpected translation key: ${key} - this won't be used!`;
+            }
+        }
+        for (const key of expectedKeys) {
+            if (!presentKeys.includes(key)) {
+                logWarn`(${code}) Missing translation key: ${key} - this won't be localized!`;
+            }
+        }
+    }
+
+    // Valid8tion is complete, 8ut We can still do a little caching to make
+    // repeated actions faster.
+
+    // We're gonna 8e mut8ting the strings dictionary o8ject from here on out.
+    // We make a copy so we don't mess with the one which was given to us.
+    stringsJSON = Object.assign({}, stringsJSON);
+
+    // Preemptively pass everything through HTML encoding. This will prevent
+    // strings from embedding HTML tags or accidentally including characters
+    // that throw HTML parsers off.
+    for (const key of Object.keys(stringsJSON)) {
+        stringsJSON[key] = he.encode(stringsJSON[key], {useNamedReferences: true});
+    }
+
+    // It's time to cre8te the actual langauge function!
+
+    // In the function, we don't actually distinguish 8etween the primary and
+    // default (fall8ack) strings - any relevant warnings have already 8een
+    // presented a8ove, at the time the language JSON is processed. Now we'll
+    // only 8e using them for indexing strings to use as templ8tes, and we can
+    // com8ine them for that.
+    const stringIndex = Object.assign({}, defaultJSON, stringsJSON);
+
+    // We do still need the list of valid keys though. That's 8ased upon the
+    // default strings. (Or stringsJSON, 8ut only if the defaults aren't
+    // provided - which indic8tes that the single o8ject provided *is* the
+    // default.)
+    const validKeys = Object.keys(defaultJSON || stringsJSON);
+
+    const invalidKeysFound = [];
+
+    const strings = (key, args = {}) => {
+        // Ok, with the warning out of the way, it's time to get to work.
+        // First make sure we're even accessing a valid key. (If not, return
+        // an error string as su8stitute.)
+        if (!validKeys.includes(key)) {
+            // We only want to warn a8out a given key once. More than that is
+            // just redundant!
+            if (!invalidKeysFound.includes(key)) {
+                invalidKeysFound.push(key);
+                logError`(${code}) Accessing invalid key ${key}. Fix a typo or provide this in strings-default.json!`;
+            }
+            return `MISSING: ${key}`;
+        }
+
+        const template = stringIndex[key];
+
+        // Convert the keys on the args dict from camelCase to CONSTANT_CASE.
+        // (This isn't an OUTRAGEOUSLY versatile algorithm for doing that, 8ut
+        // like, who cares, dude?) Also, this is an array, 8ecause it's handy
+        // for the iterating we're a8out to do.
+        const processedArgs = Object.entries(args)
+            .map(([ k, v ]) => [k.replace(/[A-Z]/g, '_$&').toUpperCase(), v]);
+
+        // Replacement time! Woot. Reduce comes in handy here!
+        const output = processedArgs.reduce(
+            (x, [ k, v ]) => x.replaceAll(`{${k}}`, v),
+            template);
+
+        // Post-processing: if any expected arguments *weren't* replaced, that
+        // is almost definitely an error.
+        if (output.match(/\{[A-Z_]+\}/)) {
+            logError`(${code}) Args in ${key} were missing - output: ${output}`;
+        }
+
+        return output;
+    };
+
+    // And lastly, we add some utility stuff to the strings function.
+
+    // Store the language code, for convenience of access.
+    strings.code = code;
+
+    // Store the strings dictionary itself, also for convenience.
+    strings.json = stringsJSON;
+
+    // Store Intl o8jects that can 8e reused for value formatting.
+    strings.intl = {
+        date: new Intl.DateTimeFormat(code, {full: true}),
+        number: new Intl.NumberFormat(code),
+        list: {
+            conjunction: new Intl.ListFormat(code, {type: 'conjunction'}),
+            disjunction: new Intl.ListFormat(code, {type: 'disjunction'}),
+            unit: new Intl.ListFormat(code, {type: 'unit'})
+        },
+        plural: {
+            cardinal: new Intl.PluralRules(code, {type: 'cardinal'}),
+            ordinal: new Intl.PluralRules(code, {type: 'ordinal'})
+        }
+    };
+
+    const bindOpts = (obj, bind) => Object.fromEntries(Object.entries(obj).map(
+        ([ key, fn ]) => [key, (value, opts = {}) => fn(value, {...bind, ...opts})]
+    ));
+
+    // And the provided utility dictionaries themselves, of course!
+    for (const [key, utilDict] of Object.entries(bindUtilities)) {
+        strings[key] = bindOpts(utilDict, {strings});
+    }
+
+    return strings;
+}