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

namespace ShrinkModFramework
{
    internal static class ShrinkModDependencyGraph
    {
        internal static void ValidateVersion(ShrinkModInfo owner, ShrinkModDependency dependency, string actual)
        {
            if (!string.IsNullOrWhiteSpace(dependency.VersionRange) && !ShrinkModVersionRange.Parse(dependency.VersionRange).Contains(actual))
                throw new InvalidOperationException($"Mod {owner.ModId} requires {dependency.ModId} in range {dependency.VersionRange}, but found {actual}.");
        }

        internal static IEnumerable<string> Predecessors(string id, IEnumerable<ShrinkModInfo> infos)
        {
            var map = infos.ToDictionary(info => info.ModId, StringComparer.Ordinal);
            foreach (var owner in map.Values)
                foreach (var dependency in owner.Dependencies)
                {
                    if (!map.ContainsKey(dependency.ModId)) continue;
                    if (owner.ModId == id && dependency.Ordering == ShrinkModDependencyOrdering.After)
                        yield return dependency.ModId;
                    if (dependency.ModId == id && dependency.Ordering == ShrinkModDependencyOrdering.Before)
                        yield return owner.ModId;
                }
        }

        internal static IReadOnlyList<ShrinkModInfo> Order(IEnumerable<ShrinkModInfo> infos)
        {
            var map = infos.ToDictionary(info => info.ModId, StringComparer.Ordinal);
            foreach (var owner in map.Values)
                foreach (var dependency in owner.Dependencies)
                {
                    if (map.TryGetValue(dependency.ModId, out var target)) ValidateVersion(owner, dependency, target.Version);
                    else if (!dependency.Optional)
                        throw new InvalidOperationException($"Mod {owner.ModId} is missing required dependency {dependency.ModId}.");
                }
            var result = new List<ShrinkModInfo>();
            var visiting = new HashSet<string>(StringComparer.Ordinal);
            var visited = new HashSet<string>(StringComparer.Ordinal);
            void Visit(string id)
            {
                if (visited.Contains(id)) return;
                if (!visiting.Add(id)) throw new InvalidOperationException($"Circular mod dependency/Before/After ordering includes {id}.");
                foreach (var predecessor in Predecessors(id, map.Values).OrderBy(value => value, StringComparer.Ordinal)) Visit(predecessor);
                visiting.Remove(id); visited.Add(id); result.Add(map[id]);
            }
            foreach (var info in map.Values.OrderBy(info => info.LoadOrder).ThenBy(info => info.ModId, StringComparer.Ordinal)) Visit(info.ModId);
            return result;
        }

        internal static bool SameMetadata(ShrinkModInfo a, ShrinkModInfo b) =>
            a.ModId == b.ModId && a.DisplayName == b.DisplayName && a.Version == b.Version &&
            a.LoadOrder == b.LoadOrder && a.EntryType == b.EntryType && a.AutoApplyHarmonyPatches == b.AutoApplyHarmonyPatches &&
            a.Dependencies.Count == b.Dependencies.Count && a.Dependencies.Zip(b.Dependencies, (x, y) =>
                x.ModId == y.ModId && x.VersionRange == y.VersionRange && x.Optional == y.Optional && x.Ordering == y.Ordering).All(equal => equal);
    }
}