using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Text.Json.Serialization;

namespace FileExposer.Models;

public record Review(Segment[]? AreEqual,
                     Segment[]? LeftSideIsNewer,
                     Segment[]? LeftSideOnly,
                     Segment[]? NotEqualBut,
                     Record[]? Records,
                     Segment[]? RightSideIsNewer,
                     Segment[]? RightSideOnly)
{

    internal static Review Get(RelativePath relativePath, ReadOnlyCollection<Record> records)
    {
        Review result;
        ReadOnlyCollection<Segment> areEqual = GetAreEqual(relativePath, records);
        ReadOnlyCollection<Segment> notEqualBut = GetNotEqualBut(relativePath, records);
        ReadOnlyCollection<Segment> leftSideOnly = GetLeftSideOnly(relativePath, records);
        ReadOnlyCollection<Segment> rightSideOnly = GetRightSideOnly(relativePath, records);
        ReadOnlyCollection<Segment> leftSideIsNewer = GetLeftSideIsNewer(relativePath, records);
        ReadOnlyCollection<Segment> rightSideIsNewer = GetRightSideIsNewer(relativePath, records);
        result = new(AreEqual: [.. areEqual],
                     LeftSideIsNewer: [.. leftSideIsNewer],
                     LeftSideOnly: [.. leftSideOnly],
                     NotEqualBut: [.. notEqualBut],
                     Records: null,
                     RightSideIsNewer: [.. rightSideIsNewer],
                     RightSideOnly: [.. rightSideOnly]);
        return result;
    }

    private static ReadOnlyCollection<Segment> GetAreEqual(RelativePath relativePath, ReadOnlyCollection<Record> records)
    {
        List<Segment> results = [];
        Segment segment;
        double totalSeconds;
        ReadOnlyDictionary<string, Record> keyValuePairs = GetKeyValuePairs(relativePath);
        foreach (Record r in records)
        {
            if (!keyValuePairs.TryGetValue(r.RelativePath, out Record? record))
                continue;
            totalSeconds = new TimeSpan(record.Ticks - r.Ticks).TotalSeconds;
            if (record.Size != r.Size || totalSeconds is > 2 or < -2)
                continue;
            segment = new(Left: r, Right: record);
            results.Add(segment);
        }
        return results.AsReadOnly();
    }

    private static ReadOnlyDictionary<string, Record> GetKeyValuePairs(RelativePath relativePath) =>
        GetKeyValuePairs(relativePath.Records.AsReadOnly());

    private static ReadOnlyDictionary<string, Record> GetKeyValuePairs(ReadOnlyCollection<Record> records)
    {
        Dictionary<string, Record> results = [];
        foreach (Record record in records)
            results.Add(record.RelativePath, record);
        return new(results);
    }

    private static ReadOnlyCollection<Segment> GetNotEqualBut(RelativePath relativePath, ReadOnlyCollection<Record> records)
    {
        List<Segment> results = [];
        Segment segment;
        double totalSeconds;
        ReadOnlyDictionary<string, Record> keyValuePairs = GetKeyValuePairs(relativePath);
        foreach (Record r in records)
        {
            if (!keyValuePairs.TryGetValue(r.RelativePath, out Record? record))
                continue;
            if (record.Size == r.Size)
                continue;
            totalSeconds = new TimeSpan(record.Ticks - r.Ticks).TotalSeconds;
            if (totalSeconds is >= 2 or <= -2)
                continue;
            segment = new(Left: r, Right: record);
            results.Add(segment);
        }
        return results.AsReadOnly();
    }

    private static ReadOnlyCollection<Segment> GetLeftSideOnly(RelativePath relativePath, ReadOnlyCollection<Record> records)
    {
        List<Segment> results = [];
        Segment segment;
        ReadOnlyDictionary<string, Record> keyValuePairs = GetKeyValuePairs(relativePath);
        foreach (Record r in records)
        {
            if (keyValuePairs.TryGetValue(r.RelativePath, out Record? record))
                continue;
            segment = new(Left: r, Right: record);
            results.Add(segment);
        }
        return results.AsReadOnly();
    }

    private static ReadOnlyCollection<Segment> GetRightSideOnly(RelativePath relativePath, ReadOnlyCollection<Record> records)
    {
        List<Segment> results = [];
        Segment segment;
        ReadOnlyDictionary<string, Record> keyValuePairs = GetKeyValuePairs(records);
        foreach (Record r in relativePath.Records)
        {
            if (keyValuePairs.TryGetValue(r.RelativePath, out Record? record))
                continue;
            segment = new(Left: record, Right: r);
            results.Add(segment);
        }
        return results.AsReadOnly();
    }

    private static ReadOnlyCollection<Segment> GetLeftSideIsNewer(RelativePath relativePath, ReadOnlyCollection<Record> records)
    {
        List<Segment> results = [];
        Segment segment;
        double totalSeconds;
        ReadOnlyDictionary<string, Record> keyValuePairs = GetKeyValuePairs(relativePath);
        foreach (Record r in records)
        {
            if (!keyValuePairs.TryGetValue(r.RelativePath, out Record? record))
                continue;
            totalSeconds = new TimeSpan(record.Ticks - r.Ticks).TotalSeconds;
            if (totalSeconds is > -2)
                continue;
            segment = new(Left: r, Right: record);
            results.Add(segment);
        }
        return results.AsReadOnly();
    }

    private static ReadOnlyCollection<Segment> GetRightSideIsNewer(RelativePath relativePath, ReadOnlyCollection<Record> records)
    {
        List<Segment> results = [];
        Segment segment;
        double totalSeconds;
        ReadOnlyDictionary<string, Record> keyValuePairs = GetKeyValuePairs(records);
        foreach (Record r in relativePath.Records)
        {
            if (!keyValuePairs.TryGetValue(r.RelativePath, out Record? record))
                continue;
            totalSeconds = new TimeSpan(record.Ticks - r.Ticks).TotalSeconds;
            if (totalSeconds is > -2)
                continue;
            segment = new(Left: record, Right: r);
            results.Add(segment);
        }
        return results.AsReadOnly();
    }

}

[JsonSourceGenerationOptions(WriteIndented = true)]
[JsonSerializable(typeof(Review))]
public partial class ReviewSourceGenerationContext : JsonSerializerContext
{
}