i18n data is kept in and generated from JSON files

Introduced a new resource compiler script kiwix-compile-i18n that
processes i18n string data stored in JSON files and generates sorted C++
tables of string keys and values for all languages.

scripts/kiwix-compile-i18n

@@ -0,0 +1,161 @@
+#!/usr/bin/env python3
+
+'''
+Copyright 2022 Veloman Yunkan <veloman.yunkan@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3 of the License, or any
+later version.
+
+This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA.
+'''
+
+import argparse
+import os.path
+import re
+import json
+
+def to_identifier(name):
+    ident = re.sub(r'[^0-9a-zA-Z]', '_', name)
+    if ident[0].isnumeric():
+        return "_"+ident
+    return ident
+
+def lang_code(filename):
+    filename = os.path.basename(filename)
+    lang = to_identifier(os.path.splitext(filename)[0])
+    print(filename, '->', lang)
+    return lang
+
+from string import Template
+
+def expand_cxx_template(t, **kwargs):
+    return Template(t).substitute(**kwargs)
+
+def cxx_string_literal(s):
+    # Taking advantage of the fact the JSON string escape rules match
+    # those of C++
+    return 'u8' + json.dumps(s)
+
+string_table_cxx_template = '''
+const I18nString $TABLE_NAME[] = {
+  $TABLE_ENTRIES
+};
+'''
+
+lang_table_entry_cxx_template = '''
+    {
+        $LANG_STRING_LITERAL,
+        ARRAY_ELEMENT_COUNT($STRING_TABLE_NAME),
+        $STRING_TABLE_NAME
+    }'''
+
+cxxfile_template = '''// This file is automatically generated. Do not modify it.
+
+#include "server/i18n.h"
+
+namespace kiwix {
+namespace i18n {
+
+namespace
+{
+
+$STRING_DATA
+
+} // unnamed namespace
+
+#define ARRAY_ELEMENT_COUNT(a) (sizeof(a)/sizeof(a[0]))
+
+extern const I18nStringTable stringTables[] = {
+  $LANG_TABLE
+};
+
+extern const size_t langCount = $LANG_COUNT;
+
+} // namespace i18n
+} // namespace kiwix
+'''
+
+class Resource:
+    def __init__(self, base_dirs, filename):
+        filename = filename.strip()
+        self.filename = filename
+        self.lang_code = lang_code(filename)
+        found = False
+        for base_dir in base_dirs:
+            try:
+                with open(os.path.join(base_dir, filename), 'r') as f:
+                    self.data = f.read()
+                found = True
+                break
+            except FileNotFoundError:
+                continue
+        if not found:
+            raise Exception("Impossible to find {}".format(filename))
+
+
+    def get_string_table_name(self):
+        return "string_table_for_" + self.lang_code
+
+    def get_string_table(self):
+        table_entries = ",\n  ".join(self.get_string_table_entries())
+        return expand_cxx_template(string_table_cxx_template,
+                    TABLE_NAME=self.get_string_table_name(),
+                    TABLE_ENTRIES=table_entries)
+
+    def get_string_table_entries(self):
+        d = json.loads(self.data)
+        for k in sorted(d.keys()):
+            if k != "@metadata":
+                key_string = cxx_string_literal(k)
+                value_string = cxx_string_literal(d[k])
+                yield '{ ' + key_string + ', ' + value_string + ' }'
+
+    def get_lang_table_entry(self):
+        return expand_cxx_template(lang_table_entry_cxx_template,
+                LANG_STRING_LITERAL=cxx_string_literal(self.lang_code),
+                STRING_TABLE_NAME=self.get_string_table_name())
+
+
+
+def gen_c_file(resources):
+    string_data = []
+    lang_table = []
+    for r in resources:
+        string_data.append(r.get_string_table())
+        lang_table.append(r.get_lang_table_entry())
+
+    return expand_cxx_template(cxxfile_template,
+                STRING_DATA="\n".join(string_data),
+                LANG_TABLE=",\n  ".join(lang_table),
+                LANG_COUNT=len(resources)
+           )
+
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--cxxfile',
+                        required=True,
+                        help='The Cpp file name to generate')
+    parser.add_argument('i18n_resource_file',
+                        help='The list of resources to compile.')
+    args = parser.parse_args()
+
+    base_dir = os.path.dirname(os.path.realpath(args.i18n_resource_file))
+    with open(args.i18n_resource_file, 'r') as f:
+        resources = [Resource([base_dir], filename)
+                        for filename in f.readlines()]
+
+    with open(args.cxxfile, 'w') as f:
+        f.write(gen_c_file(resources))
+