// A `Diff` content block, rendered as coloured hunks. ACP hands over whole
// `oldText`/`newText`, so the lines and their `+added −removed` counts are
// computed here (diff.ts) rather than parsed out of a patch.

import { useMemo } from "react";

import { computeDiffLines, diffStats, type DiffLine } from "./diff.js";
import type { AcpDiff } from "../../types.js";
import { Copyable } from "./Copyable.js";

/** Column prefix by line kind. A `hunk` summary and an `eof` marker are their
 *  own complete text, so neither takes one. */
const PREFIX: Record<DiffLine["kind"], string> = {
  add: "+ ",
  del: "- ",
  ctx: "  ",
  hunk: "",
  eof: "",
};

export function diffLineText(line: DiffLine): string {
  return PREFIX[line.kind] + line.text;
}

export interface DiffViewProps {
  diff: AcpDiff;
}

export function DiffView({ diff }: DiffViewProps) {
  const lines = useMemo(() => computeDiffLines(diff.oldText, diff.newText), [diff.oldText, diff.newText]);
  const stats = useMemo(() => diffStats(lines), [lines]);
  const plain = useMemo(() => lines.map(diffLineText).join("\n"), [lines]);

  return (
    <div className="st-diff-block">
      <Copyable className="st-diff-path" text={diff.path} label="path" title={diff.path}>
        {diff.path}
      </Copyable>
      <Copyable
        className="st-diff"
        text={plain}
        label="diff"
        data-added={stats.added}
        data-removed={stats.removed}
      >
        <pre>
          {lines.map((line, index) => (
            <span key={index} className={`st-ln st-ln-${line.kind}`}>
              {diffLineText(line)}
            </span>
          ))}
        </pre>
      </Copyable>
    </div>
  );
}