using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace CadParamPluging.Common
{
    public static class NoteTemplateEngine
    {
        public sealed class PlaceholderOccurrence
        {
            public int Index { get; set; }
            public int Start { get; set; }
            public int LineNumber { get; set; }
            public int ColumnInLine { get; set; }
            public string LineText { get; set; }
        }

        public static int CountPlaceholders(string text)
        {
            if (string.IsNullOrEmpty(text))
            {
                return 0;
            }

            var count = 0;
            for (var i = 0; i < text.Length;)
            {
                if (text[i] != '*')
                {
                    i++;
                    continue;
                }

                var j = i;
                while (j < text.Length && text[j] == '*')
                {
                    j++;
                }

                var len = j - i;
                if (len != 4)
                {
                    count += len;
                }

                i = j;
            }

            return count;
        }

        public static List<PlaceholderOccurrence> ParseOccurrences(string text)
        {
            var result = new List<PlaceholderOccurrence>();
            if (string.IsNullOrEmpty(text))
            {
                return result;
            }

            var s = NormalizeNewLines(text);

            // Keep empty lines for correct line number mapping.
            var lines = s.Split(new[] { '\n' }, StringSplitOptions.None);

            // Build line start offsets.
            var lineStartOffsets = new int[lines.Length];
            var offset = 0;
            for (var i = 0; i < lines.Length; i++)
            {
                lineStartOffsets[i] = offset;
                offset += (lines[i] ?? string.Empty).Length;
                if (i < lines.Length - 1)
                {
                    offset += 1; // '\n'
                }
            }

            var placeholderIndex = 0;
            var lineIdx = 0;
            var lineStart = lines.Length > 0 ? lineStartOffsets[0] : 0;

            for (var i = 0; i < s.Length;)
            {
                // Move line index if needed.
                while (lineIdx + 1 < lineStartOffsets.Length && i >= lineStartOffsets[lineIdx] + (lines[lineIdx] ?? string.Empty).Length + 1)
                {
                    lineIdx++;
                    lineStart = lineStartOffsets[lineIdx];
                }

                if (s[i] != '*')
                {
                    i++;
                    continue;
                }

                var j = i;
                while (j < s.Length && s[j] == '*')
                {
                    j++;
                }

                var runLen = j - i;
                if (runLen == 4)
                {
                    i = j;
                    continue;
                }

                var lineText = (lineIdx >= 0 && lineIdx < lines.Length) ? (lines[lineIdx] ?? string.Empty) : string.Empty;

                for (var k = 0; k < runLen; k++)
                {
                    placeholderIndex++;
                    var pos = i + k;
                    var col = pos - lineStart;
                    if (col < 0) col = 0;

                    result.Add(new PlaceholderOccurrence
                    {
                        Index = placeholderIndex,
                        Start = pos,
                        LineNumber = lineIdx + 1,
                        ColumnInLine = col,
                        LineText = lineText
                    });
                }

                i = j;
            }

            return result;
        }

        public static string BuildNumberedPreviewText(string templateText)
        {
            templateText = templateText ?? string.Empty;
            var s = NormalizeNewLines(templateText);

            var sb = new StringBuilder(s.Length + 64);
            var placeholderIndex = 0;

            for (var i = 0; i < s.Length;)
            {
                if (s[i] != '*')
                {
                    sb.Append(s[i]);
                    i++;
                    continue;
                }

                var j = i;
                while (j < s.Length && s[j] == '*')
                {
                    j++;
                }

                var runLen = j - i;
                if (runLen == 4)
                {
                    sb.Append("****");
                    i = j;
                    continue;
                }

                for (var k = 0; k < runLen; k++)
                {
                    placeholderIndex++;
                    sb.Append("【#");
                    sb.Append(placeholderIndex);
                    sb.Append("】");
                }

                i = j;
            }

            return sb.ToString();
        }

        public static string Render(string templateText, IEnumerable<NotePlaceholderBinding> bindings, Func<string, string> getValue)
        {
            templateText = templateText ?? string.Empty;

            var s = NormalizeNewLines(templateText);

            var map = new Dictionary<int, string>();
            foreach (var b in bindings ?? Enumerable.Empty<NotePlaceholderBinding>())
            {
                if (b == null)
                {
                    continue;
                }

                if (b.Index <= 0)
                {
                    continue;
                }

                var key = (b.ParamKey ?? string.Empty).Trim();
                if (key.Length == 0)
                {
                    continue;
                }

                if (!map.ContainsKey(b.Index))
                {
                    map[b.Index] = key;
                }
            }

            var sb = new StringBuilder(s.Length + 64);
            var placeholderIndex = 0;

            for (var i = 0; i < s.Length;)
            {
                if (s[i] != '*')
                {
                    sb.Append(s[i]);
                    i++;
                    continue;
                }

                var j = i;
                while (j < s.Length && s[j] == '*')
                {
                    j++;
                }

                var runLen = j - i;
                if (runLen == 4)
                {
                    sb.Append("****");
                    i = j;
                    continue;
                }

                for (var k = 0; k < runLen; k++)
                {
                    placeholderIndex++;
                    if (map.TryGetValue(placeholderIndex, out var key) && getValue != null)
                    {
                        var v = getValue(key);
                        if (!string.IsNullOrWhiteSpace(v))
                        {
                            sb.Append(v);
                            continue;
                        }
                    }
                    sb.Append('*');
                }

                i = j;
            }

            return sb.ToString();
        }

        /// <summary>
        /// When the same ParamKey is bound by multiple placeholders, each placeholder should have its own value key,
        /// otherwise values would overwrite each other.
        /// This method returns an equivalent bindings list where ParamKey is replaced by an effective value key.
        /// </summary>
        public static List<NotePlaceholderBinding> BuildEffectiveValueKeyBindings(IEnumerable<NotePlaceholderBinding> bindings)
        {
            var list = (bindings ?? Enumerable.Empty<NotePlaceholderBinding>())
                .Where(b => b != null && b.Index > 0 && !string.IsNullOrWhiteSpace(b.ParamKey))
                .Select(b => new NotePlaceholderBinding { Index = b.Index, ParamKey = b.ParamKey.Trim() })
                .ToList();

            var dup = list
                .GroupBy(b => b.ParamKey, StringComparer.OrdinalIgnoreCase)
                .ToDictionary(g => g.Key, g => g.Count(), StringComparer.OrdinalIgnoreCase);

            foreach (var b in list)
            {
                if (dup.TryGetValue(b.ParamKey, out var cnt) && cnt > 1)
                {
                    b.ParamKey = string.Format("{0}@{1}", b.ParamKey, b.Index);
                }
            }

            return list;
        }

        private static string NormalizeNewLines(string text)
        {
            return (text ?? string.Empty)
                .Replace("\r\n", "\n")
                .Replace("\r", "\n");
        }
    }
}