"use client";

import { useState, useRef, useCallback, useEffect } from "react";

export default function SplitView({ paragraphs, classifications, enriched }) {
  const leftRef = useRef(null);
  const rightRef = useRef(null);
  const [syncing, setSyncing] = useState(false);
  const [hoveredIndex, setHoveredIndex] = useState(null);

  // Build a lookup: paragraph index -> classification
  const classMap = new Map();
  if (classifications && classifications.length > 0) {
    for (const c of classifications) {
      classMap.set(c.index, c);
    }
  }

  // Sync scroll between panels
  const handleScroll = useCallback(
    (source) => {
      if (syncing) return;
      setSyncing(true);

      const sourceEl = source === "left" ? leftRef.current : rightRef.current;
      const targetEl = source === "left" ? rightRef.current : leftRef.current;

      if (sourceEl && targetEl) {
        const ratio =
          sourceEl.scrollTop /
          (sourceEl.scrollHeight - sourceEl.clientHeight || 1);
        targetEl.scrollTop =
          ratio * (targetEl.scrollHeight - targetEl.clientHeight);
      }

      requestAnimationFrame(() => setSyncing(false));
    },
    [syncing]
  );

  // Scroll to a paragraph on click
  const scrollToIndex = useCallback((index, panel) => {
    const ref = panel === "left" ? leftRef : rightRef;
    const el = ref.current?.querySelector(`[data-para-index="${index}"]`);
    if (el) {
      el.scrollIntoView({ behavior: "smooth", block: "center" });
    }
  }, []);

  return (
    <div className="flex-1 flex min-h-0">
      {/* Left panel: Original document view */}
      <div
        className="flex-1 flex flex-col border-r"
        style={{ borderColor: "var(--border-color)" }}
      >
        <div
          className="px-4 py-2 text-xs font-medium border-b flex items-center gap-2"
          style={{
            background: "var(--bg-tertiary)",
            borderColor: "var(--border-color)",
            color: "var(--text-secondary)",
          }}
        >
          <svg
            className="w-3.5 h-3.5"
            fill="none"
            stroke="currentColor"
            viewBox="0 0 24 24"
          >
            <path
              strokeLinecap="round"
              strokeLinejoin="round"
              strokeWidth={2}
              d="M9 12h6m-6 4h6m2 5H7a2 2 0 01-2-2V5a2 2 0 012-2h5.586a1 1 0 01.707.293l5.414 5.414a1 1 0 01.293.707V19a2 2 0 01-2 2z"
            />
          </svg>
          Original Document
        </div>
        <div
          ref={leftRef}
          className="split-panel px-4 py-3"
          onScroll={() => handleScroll("left")}
          style={{ background: "var(--bg-secondary)" }}
        >
          {paragraphs.map((p) => (
            <div
              key={`orig-${p.index}`}
              data-para-index={p.index}
              className={`para-row px-3 py-2 rounded-md mb-1 transition-colors cursor-default ${
                hoveredIndex === p.index ? "ring-1" : ""
              }`}
              style={{
                ...(hoveredIndex === p.index
                  ? {
                      background: "var(--bg-hover)",
                      ringColor: "var(--accent)",
                    }
                  : {}),
              }}
              onMouseEnter={() => setHoveredIndex(p.index)}
              onMouseLeave={() => setHoveredIndex(null)}
            >
              {p.text ? (
                <p className="text-sm leading-relaxed" style={{ color: "var(--text-primary)" }}>
                  <span
                    className="text-xs mr-2 select-none"
                    style={{ color: "var(--text-muted)" }}
                  >
                    {p.index}
                  </span>
                  {p.text}
                </p>
              ) : (
                <p className="text-sm" style={{ color: "var(--text-muted)", opacity: 0.3 }}>
                  <span className="text-xs mr-2 select-none">{p.index}</span>
                  (empty)
                </p>
              )}
              {p.fontSizePt && (
                <span
                  className="text-xs ml-6"
                  style={{ color: "var(--text-muted)" }}
                >
                  {p.fontSizePt}pt
                  {p.isBold ? " • bold" : ""}
                </span>
              )}
            </div>
          ))}
        </div>
      </div>

      {/* Right panel: Enriched view with toggle controls */}
      <div className="flex-1 flex flex-col">
        <div
          className="px-4 py-2 text-xs font-medium border-b flex items-center gap-2"
          style={{
            background: "var(--bg-tertiary)",
            borderColor: "var(--border-color)",
            color: "var(--text-secondary)",
          }}
        >
          <svg
            className="w-3.5 h-3.5"
            fill="none"
            stroke="currentColor"
            viewBox="0 0 24 24"
          >
            <path
              strokeLinecap="round"
              strokeLinejoin="round"
              strokeWidth={2}
              d="M11 5H6a2 2 0 00-2 2v11a2 2 0 002 2h11a2 2 0 002-2v-5m-1.414-9.414a2 2 0 112.828 2.828L11.828 15H9v-2.828l8.586-8.586z"
            />
          </svg>
          Enriched Document
          {enriched && (
            <span className="ml-auto text-xs" style={{ color: "var(--text-muted)" }}>
              Click checkboxes to toggle headings
            </span>
          )}
        </div>
        <div
          ref={rightRef}
          className="split-panel px-4 py-3"
          onScroll={() => handleScroll("right")}
          style={{ background: "var(--bg-secondary)" }}
        >
          {!enriched ? (
            <div className="flex items-center justify-center h-full">
              <div className="text-center">
                <div
                  className="w-16 h-16 mx-auto mb-4 rounded-full flex items-center justify-center"
                  style={{ background: "var(--bg-tertiary)" }}
                >
                  <svg
                    className="w-7 h-7"
                    style={{ color: "var(--text-muted)" }}
                    fill="none"
                    stroke="currentColor"
                    viewBox="0 0 24 24"
                  >
                    <path
                      strokeLinecap="round"
                      strokeLinejoin="round"
                      strokeWidth={1.5}
                      d="M13 10V3L4 14h7v7l9-11h-7z"
                    />
                  </svg>
                </div>
                <p
                  className="text-sm font-medium mb-1"
                  style={{ color: "var(--text-secondary)" }}
                >
                  Click &quot;Enrich with AI&quot; to start
                </p>
                <p className="text-xs" style={{ color: "var(--text-muted)" }}>
                  The AI will detect which paragraphs are headings
                </p>
              </div>
            </div>
          ) : (
            <EnrichedParagraphs
              paragraphs={paragraphs}
              classifications={classifications}
              classMap={classMap}
              hoveredIndex={hoveredIndex}
              setHoveredIndex={setHoveredIndex}
            />
          )}
        </div>
      </div>
    </div>
  );
}

function EnrichedParagraphs({
  paragraphs,
  classifications,
  classMap,
  hoveredIndex,
  setHoveredIndex,
}) {
  // We maintain local state for checkbox toggling
  // This lets users toggle headings before clicking "Apply Changes"
  const [localClassifications, setLocalClassifications] = useState(classifications);

  // Sync when parent classifications change (after enrich or apply)
  useEffect(() => {
    setLocalClassifications(classifications);
  }, [classifications]);

  const localClassMap = new Map();
  for (const c of localClassifications) {
    localClassMap.set(c.index, c);
  }

  const toggleHeading = (index) => {
    setLocalClassifications((prev) =>
      prev.map((c) =>
        c.index === index ? { ...c, isHeading: !c.isHeading } : c
      )
    );
    // Also update the parent's classifications directly so "Apply Changes" picks them up
    const existing = classMap.get(index);
    if (existing) {
      existing.isHeading = !existing.isHeading;
    }
  };

  return (
    <>
      {paragraphs.map((p) => {
        const cls = localClassMap.get(p.index);
        const isHeading = cls?.isHeading || false;

        return (
          <div
            key={`enr-${p.index}`}
            data-para-index={p.index}
            className={`para-row flex items-start gap-3 px-3 py-2 rounded-md mb-1 transition-colors ${
              isHeading ? "is-heading" : ""
            } ${hoveredIndex === p.index ? "ring-1" : ""}`}
            style={{
              ...(hoveredIndex === p.index
                ? {
                    background: "var(--bg-hover)",
                    ringColor: "var(--accent)",
                  }
                : {}),
            }}
            onMouseEnter={() => setHoveredIndex(p.index)}
            onMouseLeave={() => setHoveredIndex(null)}
          >
            <input
              type="checkbox"
              className="heading-checkbox mt-1"
              checked={isHeading}
              onChange={() => toggleHeading(p.index)}
              title={isHeading ? "Unmark as heading" : "Mark as heading"}
            />
            <div className="flex-1 min-w-0">
              {p.text ? (
                <p
                  className={`leading-relaxed ${isHeading ? "font-bold" : ""}`}
                  style={{
                    color: isHeading
                      ? "var(--accent)"
                      : "var(--text-primary)",
                    fontSize: isHeading ? "16px" : "14px",
                  }}
                >
                  <span
                    className="text-xs mr-2 font-normal select-none"
                    style={{ color: "var(--text-muted)" }}
                  >
                    {p.index}
                  </span>
                  {p.text}
                </p>
              ) : (
                <p className="text-sm" style={{ color: "var(--text-muted)", opacity: 0.3 }}>
                  <span className="text-xs mr-2 select-none">{p.index}</span>
                  (empty)
                </p>
              )}
              {isHeading && (
                <span
                  className="text-xs ml-6 inline-block mt-0.5"
                  style={{ color: "var(--accent)" }}
                >
                  ✦ Heading — font size will be increased
                </span>
              )}
            </div>
          </div>
        );
      })}
    </>
  );
}