using System.Collections.Generic;

namespace XCEngine.Rendering.Universal
{
    internal sealed class RendererBlocks
    {
        private struct BlockRange
        {
            public int firstPassIndex;
            public int lastPassIndex;
        }

        private readonly BlockRange[] m_ranges =
            new BlockRange[(int)RendererBlock.Count];

        public RendererBlocks()
        {
            Clear();
        }

        public void Clear()
        {
            for (int i = 0; i < m_ranges.Length; ++i)
            {
                m_ranges[i].firstPassIndex = -1;
                m_ranges[i].lastPassIndex = -1;
            }
        }

        public void Build(
            IList<ScriptableRenderPass> activePassQueue)
        {
            Clear();

            if (activePassQueue == null)
            {
                return;
            }

            for (int i = 0; i < activePassQueue.Count; ++i)
            {
                ScriptableRenderPass renderPass =
                    activePassQueue[i];
                if (renderPass == null)
                {
                    continue;
                }

                RendererBlock block;
                if (!ScriptableRenderPass.TryResolveRendererBlock(
                        renderPass.renderPassEvent,
                        out block))
                {
                    continue;
                }

                int blockIndex = (int)block;
                BlockRange range = m_ranges[blockIndex];
                if (range.firstPassIndex < 0)
                {
                    range.firstPassIndex = i;
                }

                range.lastPassIndex = i;
                m_ranges[blockIndex] = range;
            }
        }

        public bool HasPasses(
            RendererBlock block)
        {
            BlockRange range = m_ranges[(int)block];
            return range.firstPassIndex >= 0 &&
                   range.lastPassIndex >= range.firstPassIndex;
        }

        public bool TryGetPassRange(
            RendererBlock block,
            out int firstPassIndex,
            out int lastPassIndex)
        {
            BlockRange range = m_ranges[(int)block];
            firstPassIndex = range.firstPassIndex;
            lastPassIndex = range.lastPassIndex;
            return range.firstPassIndex >= 0 &&
                   range.lastPassIndex >= range.firstPassIndex;
        }
    }
}