using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using Ips.Eph;
using Ips.Library.Entity;

namespace Ips.Eph.ResolveUtil
{
    public static class HpeResolveUtil
    {
        const int MinColCount = 92;

        public static EphResult Parse(Span<char> line, int satid = 0)
        {
            int i = 0;
            var year = int.Parse(line.Slice(i, 5));
            i += 5;
            var month = int.Parse(line.Slice(i, 4));
            i += 4;
            var day = int.Parse(line.Slice(i, 4));
            i += 4;
            var hour = int.Parse(line.Slice(i, 4));
            i += 4;
            var minute = int.Parse(line.Slice(i, 4));
            i += 4;
            var second = float.Parse(line.Slice(i, 10));
            i += 10;

            var x = double.Parse(line.Slice(i, 20));
            i += 20;
            var y = double.Parse(line.Slice(i, 20));
            i += 20;
            var z = double.Parse(line.Slice(i, 20));
            i += 20;
            var vx = double.Parse(line.Slice(i, 20));
            i += 20;
            var vy = double.Parse(line.Slice(i, 20));
            i += 20;
            var vz = double.Parse(line.Slice(i, 20));

            var time = new DateTime(year, month, day, hour, minute, (int)second, DateTimeKind.Local).AddHours(8);
            var result = new EphResult(satid, time.ToLocalTime(), x, y, z, vx, vy, vz);
            return result;
        }

        public static EphResult Parse(char[] line, int satid = 0)
        {
            Span<char> chars = new Span<char>(line);
            return Parse(chars, satid);
        }

        public static EphResult Parse(string line, int satid = 0)
        {
            Span<char> chars = new Span<char>(line.ToCharArray());
            return Parse(chars, satid);
        }

        public static IEnumerable<EphResult> ParseFile(string filename, int satid = 0)
        {
            using (var reader = new StreamReader(filename))
            {
                Span<char> startLine = stackalloc char[300];
                reader.ReadBlock(startLine);
                var colCount = startLine.IndexOf('\n') + 1;
                if (colCount < MinColCount)
                    yield break;
                reader.BaseStream.Seek(0, SeekOrigin.Begin);
                reader.DiscardBufferedData();
                var readLen = 0;
                while (!reader.EndOfStream)
                {
                    Span<char> line = stackalloc char[colCount];
                    readLen = reader.ReadBlock(line);
                    if (readLen != colCount) continue;
                    yield return Parse(line, satid);
                }
            }
            yield break;
        }
    }
}