using System;
using System.Collections.Generic;
using System.Globalization;
using System.Text;

namespace MSCO
{
    /// <summary>
    /// Kleiner eigener JSON-Leser (ohne Newtonsoft.Json - das braucht System.Runtime.Serialization, das ohne MSCLoader im
    /// Spiel fehlt). Ergebnis: Dictionary&lt;string, object&gt; (Objekt, Schlüssel ohne Groß-/Kleinschreibung),
    /// List&lt;object&gt;, string, double, bool oder null.
    /// </summary>
    public static class MiniJson
    {
        public static object Parse(string json)
        {
            if (json == null) throw new FormatException("No JSON");
            int i = 0;
            object value = ReadValue(json, ref i);
            SkipWhitespace(json, ref i);
            if (i < json.Length) throw new FormatException("Unexpected text at " + i);
            return value;
        }

        // ---------------------------------------------------------------- Zugriff

        public static string Str(Dictionary<string, object> o, string key, string fallback = null)
        {
            object v;
            if (o == null || !o.TryGetValue(key, out v) || v == null) return fallback;
            if (v is double) return ((double)v).ToString(CultureInfo.InvariantCulture);
            return v.ToString();
        }

        public static int Int(Dictionary<string, object> o, string key, int fallback = 0)
        {
            object v;
            if (o == null || !o.TryGetValue(key, out v)) return fallback;
            if (v is double) return (int)(double)v;
            int parsed;
            return v is string && int.TryParse((string)v, NumberStyles.Integer, CultureInfo.InvariantCulture, out parsed) ? parsed : fallback;
        }

        public static bool Bool(Dictionary<string, object> o, string key, bool fallback = false)
        {
            object v;
            if (o == null || !o.TryGetValue(key, out v)) return fallback;
            return v is bool ? (bool)v : fallback;
        }

        public static List<string> Strings(Dictionary<string, object> o, string key)
        {
            var result = new List<string>();
            object v;
            if (o == null || !o.TryGetValue(key, out v)) return result;
            var list = v as List<object>;
            if (list != null) foreach (object item in list) if (item != null) result.Add(item.ToString());
            return result;
        }

        // ---------------------------------------------------------------- Lesen

        static object ReadValue(string s, ref int i)
        {
            SkipWhitespace(s, ref i);
            if (i >= s.Length) throw new FormatException("Unexpected end of JSON");
            char c = s[i];
            if (c == '{') return ReadObject(s, ref i);
            if (c == '[') return ReadArray(s, ref i);
            if (c == '"') return ReadString(s, ref i);
            if (c == '-' || (c >= '0' && c <= '9')) return ReadNumber(s, ref i);
            if (Word(s, ref i, "true")) return true;
            if (Word(s, ref i, "false")) return false;
            if (Word(s, ref i, "null")) return null;
            throw new FormatException("Unexpected '" + c + "' at " + i);
        }

        static Dictionary<string, object> ReadObject(string s, ref int i)
        {
            var o = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
            i++; // {
            SkipWhitespace(s, ref i);
            if (i < s.Length && s[i] == '}') { i++; return o; }
            while (true)
            {
                SkipWhitespace(s, ref i);
                if (i >= s.Length || s[i] != '"') throw new FormatException("Expected a name at " + i);
                string key = ReadString(s, ref i);
                SkipWhitespace(s, ref i);
                if (i >= s.Length || s[i] != ':') throw new FormatException("Expected ':' at " + i);
                i++;
                o[key] = ReadValue(s, ref i);
                SkipWhitespace(s, ref i);
                if (i >= s.Length) throw new FormatException("Unexpected end of JSON");
                if (s[i] == ',') { i++; continue; }
                if (s[i] == '}') { i++; return o; }
                throw new FormatException("Expected ',' or '}' at " + i);
            }
        }

        static List<object> ReadArray(string s, ref int i)
        {
            var list = new List<object>();
            i++; // [
            SkipWhitespace(s, ref i);
            if (i < s.Length && s[i] == ']') { i++; return list; }
            while (true)
            {
                list.Add(ReadValue(s, ref i));
                SkipWhitespace(s, ref i);
                if (i >= s.Length) throw new FormatException("Unexpected end of JSON");
                if (s[i] == ',') { i++; continue; }
                if (s[i] == ']') { i++; return list; }
                throw new FormatException("Expected ',' or ']' at " + i);
            }
        }

        static string ReadString(string s, ref int i)
        {
            var sb = new StringBuilder();
            i++; // "
            while (i < s.Length)
            {
                char c = s[i++];
                if (c == '"') return sb.ToString();
                if (c != '\\') { sb.Append(c); continue; }
                if (i >= s.Length) break;
                char e = s[i++];
                switch (e)
                {
                    case 'b': sb.Append('\b'); break;
                    case 'f': sb.Append('\f'); break;
                    case 'n': sb.Append('\n'); break;
                    case 'r': sb.Append('\r'); break;
                    case 't': sb.Append('\t'); break;
                    case 'u':
                        if (i + 4 > s.Length) throw new FormatException("Bad \\u escape");
                        sb.Append((char)int.Parse(s.Substring(i, 4), NumberStyles.HexNumber, CultureInfo.InvariantCulture));
                        i += 4;
                        break;
                    default: sb.Append(e); break; // \" \\ \/
                }
            }
            throw new FormatException("Unterminated string");
        }

        static double ReadNumber(string s, ref int i)
        {
            int start = i;
            while (i < s.Length && "+-0123456789.eE".IndexOf(s[i]) >= 0) i++;
            return double.Parse(s.Substring(start, i - start), NumberStyles.Float, CultureInfo.InvariantCulture);
        }

        static bool Word(string s, ref int i, string word)
        {
            if (string.CompareOrdinal(s, i, word, 0, word.Length) != 0) return false;
            i += word.Length;
            return true;
        }

        static void SkipWhitespace(string s, ref int i)
        {
            while (i < s.Length && char.IsWhiteSpace(s[i])) i++;
        }
    }
}