zedseven/Romanization.NET

using System;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.IO;

namespace Romanization.Internal
{
    /// <summary>
    /// For systems whose conversion charts are too large to reasonably pack in-DLL, they're stored in separate CSV
    /// files and loaded in upon construction of the system.<br />
    /// A good example of this is <see cref="Chinese.HanyuPinyin"/> - the Hànyǔ Pīnyīn chart alone has over 30000
    /// characters.
    /// </summary>
    internal static class CsvLoader
    {
        public static readonly string LanguageCharacterMapsPath = Path.Combine(Constants.AssemblyPath,
            "contentFiles", "any", "any", "LanguageCharacterMaps");

        /// <summary>
        /// Loads a language character map file into a dictionary, using the provided mapping functions to map CSV entries to dict keys &amp; values.
        /// </summary>
        /// <typeparam name="TKey">The type of the dictionary keys.</typeparam>
        /// <typeparam name="TVal">The type of the dictionary values.</typeparam>
        /// <param name="fileName">The file name of the language character map file.</param>
        /// <param name="dict">The dictionary to load into.</param>
        /// <param name="keyMapper">The function that maps CSV entry first values to dictionary <typeparamref name="TKey"/> values.</param>
        /// <param name="valueMapper">The function that maps CSV entry second values to dictionary <typeparamref name="TVal"/> values.</param>
        /// <exception cref="T:Romanization.Internal.CannotReadStreamException">The provided stream cannot be read.</exception>
        /// <exception cref="T:Romanization.Internal.CsvLoadingException">Unable to load the CSV file.</exception>
        public static void LoadCharacterMap<TKey, TVal>(string fileName, IDictionary<TKey, TVal> dict, Func<string, TKey> keyMapper, Func<string, TVal> valueMapper)
        {
            using FileStream csvStream = File.OpenRead(Path.Combine(LanguageCharacterMapsPath, fileName));
            csvStream.LoadCsvIntoDictionary(dict, keyMapper, valueMapper);
        }

        /// <summary>
        /// Loads a CSV file stream into a dictionary, using the provided mapping functions to map CSV entries to dict
        /// keys &amp; values.<br />
        /// Note that this is a non-standard CSV parsing implementation - it only looks for the first comma.
        /// </summary>
        /// <typeparam name="TKey">The type of the dictionary keys.</typeparam>
        /// <typeparam name="TVal">The type of the dictionary values.</typeparam>
        /// <param name="stream">The CSV file stream.</param>
        /// <param name="dict">The dictionary to load into.</param>
        /// <param name="keyMapper">The function that maps CSV entry first values to dictionary <typeparamref name="TKey"/> values.</param>
        /// <param name="valueMapper">The function that maps CSV entry second values to dictionary <typeparamref name="TVal"/> values.</param>
        /// <exception cref="T:Romanization.Internal.CannotReadStreamException">The provided stream cannot be read.</exception>
        /// <exception cref="T:Romanization.Internal.CsvLoadingException">Unable to load the CSV file.</exception>
        public static void LoadCsvIntoDictionary<TKey, TVal>(this FileStream stream, IDictionary<TKey, TVal> dict, Func<string, TKey> keyMapper, Func<string, TVal> valueMapper)
        {
            if (!stream.CanRead)
                throw new CannotReadStreamException("The provided stream cannot be read.", nameof(stream));

            try
            {
                using StreamReader reader = new StreamReader(stream);

                // Discard the first line, since it's simply the heading
                _ = reader.ReadLine();

                while (!reader.EndOfStream)
                {
                    string line = reader.ReadLine();
                    if (string.IsNullOrWhiteSpace(line))
                        continue;

                    int commaIndex = line.IndexOf(',');
                    if (commaIndex < 0)
                        continue;

                    dict[keyMapper(line.Substring(0, commaIndex))] =
                        valueMapper(line.Substring(commaIndex + 1));
                }
            }
            catch (Exception e)
            {
                throw new CsvLoadingException("Unable to load the CSV file.", e);
            }
        }

        [Pure]
        private static string WithoutQuotes(this string str)
            => str.Length >= 2 && str[0] == '"' && str[^1] == '"' ? str[1..^1] : str;
    }
}