import {
  type ClipboardEventHandler,
  type KeyboardEvent,
  useLayoutEffect,
  useRef,
} from 'react';

const DRAFT_MIN_HEIGHT_PX = 40;
const DRAFT_MAX_HEIGHT_PX = 128;

// for fallback on some browser
function supportsNativeFieldSizing() {
  return (
    typeof CSS !== 'undefined' &&
    typeof CSS.supports === 'function' &&
    CSS.supports('field-sizing', 'content')
  );
}

function resizeFallbackTextarea(textarea: HTMLTextAreaElement) {
  textarea.style.height = 'auto';
  const contentHeight = textarea.scrollHeight;
  const borderHeight = Math.max(
    0,
    textarea.offsetHeight - textarea.clientHeight,
  );
  const borderBoxContentHeight = contentHeight + borderHeight;
  const nextHeight = Math.min(
    Math.max(borderBoxContentHeight, DRAFT_MIN_HEIGHT_PX),
    DRAFT_MAX_HEIGHT_PX,
  );
  textarea.style.height = `${nextHeight}px`;
  textarea.style.overflowY =
    borderBoxContentHeight > DRAFT_MAX_HEIGHT_PX ? 'auto' : 'hidden';
}

export function EditorAgentDraftTextarea({
  value,
  onChange,
  onPaste,
}: {
  value: string;
  onChange: (value: string) => void;
  onPaste?: ClipboardEventHandler<HTMLTextAreaElement>;
}) {
  const textareaRef = useRef<HTMLTextAreaElement>(null);

  useLayoutEffect(() => {
    const textarea = textareaRef.current;
    if (!textarea || supportsNativeFieldSizing()) {
      return;
    }
    resizeFallbackTextarea(textarea);
  }, [value]);

  useLayoutEffect(() => {
    const textarea = textareaRef.current;
    if (!textarea || supportsNativeFieldSizing()) {
      return undefined;
    }

    let previousWidth = textarea.getBoundingClientRect().width;
    const resizeWhenWidthChanges = (nextWidth: number) => {
      if (Math.abs(nextWidth - previousWidth) < 0.5) {
        return;
      }
      previousWidth = nextWidth;
      resizeFallbackTextarea(textarea);
    };

    if (typeof ResizeObserver !== 'undefined') {
      const observer = new ResizeObserver((entries) => {
        const entry = entries[0];
        if (entry) {
          resizeWhenWidthChanges(entry.contentRect.width);
        }
      });
      observer.observe(textarea);
      return () => observer.disconnect();
    }

    const handleWindowResize = () => {
      resizeWhenWidthChanges(textarea.getBoundingClientRect().width);
    };
    window.addEventListener('resize', handleWindowResize);
    return () => window.removeEventListener('resize', handleWindowResize);
  }, []);

  const handleKeyDown = (event: KeyboardEvent<HTMLTextAreaElement>) => {
    if (event.key === 'Enter' && !event.shiftKey) {
      event.preventDefault();
      event.currentTarget.form?.requestSubmit();
    }
  };

  return (
    <textarea
      ref={textareaRef}
      className="editor-agent-conversation__draft-input max-h-32 min-h-10 min-w-0 flex-1 resize-none overflow-x-hidden overflow-y-auto overscroll-contain rounded-3xl border border-slate-200 bg-slate-50 px-3 py-2 text-sm text-slate-800 outline-none [field-sizing:content] focus:border-slate-400"
      aria-label="发送给画布 Agent"
      value={value}
      rows={1}
      onChange={(event) => onChange(event.currentTarget.value)}
      onPaste={onPaste}
      onKeyDown={handleKeyDown}
    />
  );
}