package net.minecraft.client.input;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableList.Builder;
import java.nio.IntBuffer;
import java.util.List;
import net.fabricmc.api.EnvType;
import net.fabricmc.api.Environment;
import net.minecraft.network.chat.Component;
import net.minecraft.network.chat.MutableComponent;
import net.minecraft.network.chat.Style;
import org.jspecify.annotations.Nullable;
import org.lwjgl.system.MemoryUtil;

@Environment(EnvType.CLIENT)
public record PreeditEvent(String fullText, int caretPosition, List<String> blocks, int focusedBlock) {
	public PreeditEvent(String fullText, int caretPosition, List<String> blocks, int focusedBlock) {
		Preconditions.checkElementIndex(focusedBlock, blocks.size());
		this.fullText = fullText;
		this.caretPosition = caretPosition;
		this.blocks = blocks;
		this.focusedBlock = focusedBlock;
	}

	@Nullable
	public static PreeditEvent createFromCallback(
		final int preeditSize, final long preeditPtr, final int blockCount, final long blockSizesPtr, final int focusedBlock, final int caret
	) {
		if (preeditSize == 0) {
			return null;
		} else {
			int[] codepoints = readIntBuffer(preeditSize, preeditPtr);
			int[] blockSizes = readIntBuffer(blockCount, blockSizesPtr);
			StringBuilder fullText = new StringBuilder();
			Builder<String> blocks = ImmutableList.builder();
			int offset = 0;
			int convertedCaret = 0;

			for (int blockSize : blockSizes) {
				StringBuilder blockBuilder = new StringBuilder();

				for (int i = 0; i < blockSize; i++) {
					int codepoint = codepoints[offset];
					if (offset == caret) {
						convertedCaret = fullText.length() + blockBuilder.length();
					}

					blockBuilder.appendCodePoint(codepoint);
					offset++;
				}

				String block = blockBuilder.toString();
				blocks.add(block);
				fullText.append(block);
			}

			if (offset == caret) {
				convertedCaret = fullText.length();
			}

			return new PreeditEvent(fullText.toString(), convertedCaret, blocks.build(), focusedBlock);
		}
	}

	private static int[] readIntBuffer(final int size, final long ptr) {
		IntBuffer buffer = MemoryUtil.memIntBuffer(ptr, size);
		int[] result = new int[size];
		buffer.get(result);
		return result;
	}

	public MutableComponent toFormattedText(final Style focusedStyle) {
		int blockCount = this.blocks.size();
		if (blockCount == 1) {
			return Component.literal((String)this.blocks.getFirst()).withStyle(focusedStyle);
		} else {
			MutableComponent result = Component.empty();

			for (int i = 0; i < blockCount; i++) {
				MutableComponent part = Component.literal((String)this.blocks.get(i));
				if (i == this.focusedBlock) {
					part.withStyle(focusedStyle);
				}

				result.append(part);
			}

			return result;
		}
	}
}