using System;
using System.Collections.Generic;
using System.Linq;
using Debug = UnityEngine.Debug;
using OHM.UnityToolkit;

public static class LevelGenerator
{
	public static List<Section> GenerateLevel(CoreDef def, long levelIdx, Random random, List<Section> forceLevel, List<Section> previousSections)
	{
		var result = new List<Section>();
		ProgressionDef progression = def.GetProgression();
		if (progression.initialSection != null)
		{
			result.Add(progression.initialSection);
		}
		if (forceLevel != null && forceLevel.Count >= 1)
		{
			result.AddRange(forceLevel);
		}
		else
		{
			result.AddRange(GetLevelSectionList(def, levelIdx, random, previousSections));
		}
		Section final = progression.finalSectionABTest;
		if (final != null)
		{
			result.Add(final);
		}
		return result;
	}

	private static List<Section> GetLevelSectionList(CoreDef def, long levelIdx, Random random, List<Section> sectionsToAvoid)
	{
		ProgressionDef progression = def.GetProgression();
		LevelDef level = def.GetLevel(levelIdx);
		var pool = new List<Section>(progression.sections);
		var result = new List<Section>();

		if (sectionsToAvoid != null && sectionsToAvoid.Count >= 1)
		{
			pool.RemoveAll((Section s) => sectionsToAvoid.Contains(s));
		}
		foreach (Section forced in level.forcedSections)
		{
			if (forced != null)
			{
				result.Add(forced);
				pool.Remove(forced);
			}
		}
		for (int i = result.Count; i < level.sectionCount; i++)
		{
			Section drawn = DrawSection(level, def, i, levelIdx, pool, random, level.maxSectionYPerLevel);
			if (drawn != null)
			{
				result.Add(drawn);
				pool.Remove(drawn);
			}
		}
		return result;
	}

	private static Section DrawSection(LevelDef level, CoreDef coreDef, int index, long levelIdx, List<Section> currentSectionsPool, Random random, int maxSectionYPerLevel)
	{
		var diffPool = new List<DifficultyPoolElem>(
			(level.randomDiffPoolAlt != null && level.randomDiffPoolAlt.Count >= 1 && index % 2 == 1)
				? level.randomDiffPoolAlt
				: level.randomDiffPool);

		if (maxSectionYPerLevel <= 0)
		{
			foreach (DifficultyPoolElem elem in new List<DifficultyPoolElem>(diffPool))
			{
				List<Section> match = currentSectionsPool.Where((Section s) => s.difficulty == elem.element).ToList();
				if (match.Count >= 1 && match[0].differentPath)
				{
					diffPool.Remove(elem);
				}
			}
		}

		int difficulty = RandomPoolUtils.DrawElementFromPool<DifficultyPoolElem, int>(random, diffPool);
		List<Section> candidates = currentSectionsPool.Where((Section s) => s.difficulty == difficulty).ToList();
		if (candidates.Count != 0)
		{
			return RandomExtensions.ListElem(random, candidates);
		}

		Debug.LogFormat("No more section with diff {0}", difficulty);
		List<Section> fallback = currentSectionsPool.Where((Section s) => s.difficulty != difficulty).ToList();
		if (fallback.Count == 0)
		{
			return null;
		}
		Debug.LogWarningFormat("No section with difficulty {0} found, referenced in level {1}. Will use random other difficulty.", difficulty, levelIdx);
		return RandomExtensions.ListElem(random, fallback);
	}
}