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

/**
 * The notes for a page, written in the margin beside it.
 *
 * This is where a reader has always put remarks: level with the passage, in the
 * white space, not over the words. Writing them onto the page would cover the
 * sentence the note is about, which is the one thing a note about a sentence
 * must not do.
 *
 * Each card sits at the height of its anchor. Cards keep one height so that two
 * notes close together can be laid out without measuring: they are simply pushed
 * down until they no longer overlap, and the marker's hairline still says which
 * spot each belongs to. The card being written in grows and rises above the
 * others, because that one is being read closely and the rest are not.
 */

export const MARGIN_W = 208;
const CARD_H = 74;
const CARD_GAP = 6;

/** Cards at their anchors, pushed down where they would sit on top of each other. */
function layout(notes, pageHeight, cssHeight) {
  let previousBottom = -Infinity;
  return notes
    .slice()
    .sort((a, b) => a.y - b.y)
    .map((note) => {
      const anchor = (note.y / pageHeight) * cssHeight - 12;
      const top = Math.max(anchor, previousBottom + CARD_GAP);
      previousBottom = top + CARD_H;
      return { note, top };
    });
}

function Card({ T, note, top, number, open, onOpen, onChange, onRemove }) {
  const [draft, setDraft] = useState(note.text);
  const areaRef = useRef(null);

  // Adopt text that arrived from elsewhere — another device, or an undo — but
  // never while this card is the one being typed into.
  useEffect(() => {
    if (!open) setDraft(note.text);
  }, [note.text, open]);

  useEffect(() => {
    if (open) areaRef.current?.focus();
  }, [open]);

  // Committed on the way out, not per keystroke: every save rewrites the whole
  // overlay, and one per character would be absurd.
  const commit = () => {
    if (draft !== note.text) onChange(draft);
  };

  return (
    <div
      data-pin-card={note.id}
      onClick={() => !open && onOpen(note.id)}
      style={{
        position: "absolute",
        left: 0,
        right: 0,
        top,
        zIndex: open ? 5 : 1,
        display: "flex",
        gap: 6,
        padding: 8,
        borderRadius: 10,
        border: `1px solid ${open ? T.accent : T.border}`,
        background: T.bar,
        boxShadow: open ? "0 8px 22px rgba(0,0,0,.28)" : "none",
        cursor: open ? "default" : "pointer",
      }}
    >
      <span
        style={{
          flexShrink: 0,
          width: 18,
          height: 18,
          borderRadius: "50%",
          background: T.accent,
          color: "#fff",
          fontSize: 10.5,
          fontWeight: 700,
          display: "flex",
          alignItems: "center",
          justifyContent: "center",
        }}
      >
        {number}
      </span>

      <div style={{ flex: 1, minWidth: 0 }}>
        {open ? (
          <>
            <textarea
              ref={areaRef}
              value={draft}
              onChange={(e) => setDraft(e.target.value)}
              onBlur={commit}
              onKeyDown={(e) => {
                e.stopPropagation();
                if (e.key === "Escape") {
                  commit();
                  onOpen(null);
                }
              }}
              aria-label="Pinned note"
              placeholder="Notiz zu dieser Stelle…"
              rows={4}
              style={{
                width: "100%",
                resize: "vertical",
                border: `1px solid ${T.border}`,
                borderRadius: 8,
                background: "transparent",
                color: T.text,
                fontSize: 11.5,
                lineHeight: 1.5,
                padding: "5px 7px",
                outline: "none",
                fontFamily: "inherit",
              }}
            />
            <div style={{ display: "flex", alignItems: "center", marginTop: 5 }}>
              <button
                onClick={onRemove}
                data-pin-remove
                style={{
                  border: "none",
                  background: "transparent",
                  color: T.danger,
                  cursor: "pointer",
                  fontSize: 10.5,
                  padding: 0,
                }}
              >
                Entfernen
              </button>
              <span style={{ flex: 1 }} />
              <button
                onClick={() => {
                  commit();
                  onOpen(null);
                }}
                style={{
                  border: "none",
                  background: T.accent,
                  color: "#fff",
                  borderRadius: 7,
                  cursor: "pointer",
                  fontSize: 10.5,
                  fontWeight: 600,
                  padding: "3px 10px",
                }}
              >
                Fertig
              </button>
            </div>
          </>
        ) : (
          <div
            style={{
              fontSize: 11.5,
              lineHeight: 1.45,
              color: note.text ? T.text : T.muted,
              maxHeight: CARD_H - 22,
              overflow: "hidden",
              display: "-webkit-box",
              WebkitLineClamp: 3,
              WebkitBoxOrient: "vertical",
              wordBreak: "break-word",
            }}
          >
            {note.text || "Leer — zum Schreiben antippen"}
          </div>
        )}
      </div>
    </div>
  );
}

export function PdfMargin({ T, notes, pageHeight, cssHeight, openId, onOpen, onChange, onRemove, numberOf }) {
  const placed = layout(notes, pageHeight, cssHeight);
  // Cards near the foot of a page may need more room than the page is tall.
  const needed = placed.length ? placed[placed.length - 1].top + CARD_H : 0;

  return (
    <div
      data-pdf-margin
      style={{
        position: "relative",
        width: MARGIN_W,
        flexShrink: 0,
        minHeight: Math.max(cssHeight, needed),
      }}
    >
      {placed.map(({ note, top }) => (
        <Card
          key={note.id}
          T={T}
          note={note}
          top={top}
          number={numberOf(note.id)}
          open={openId === note.id}
          onOpen={onOpen}
          onChange={(text) => onChange(note.id, text)}
          onRemove={() => onRemove(note.id)}
        />
      ))}
    </div>
  );
}