import { useEffect, useState } from 'react';
import type { DiffResult } from '../../lib/orchestratorApi';

/**
 * Overlay showing a run's branch diff against main — the commits it would
 * bring in, a `--stat` summary, and the full (size-capped) patch — so the
 * operator can review an agent's work before merging it.
 */

interface DiffModalProps {
  /** Fetch the diff; throws on a missing worktree. */
  load: () => Promise<DiffResult>;
  onClose: () => void;
}

export function DiffModal({ load, onClose }: DiffModalProps) {
  const [diff, setDiff] = useState<DiffResult | null>(null);
  const [error, setError] = useState<string | null>(null);

  useEffect(() => {
    let cancelled = false;
    setError(null);
    setDiff(null);
    load()
      .then((d) => {
        if (!cancelled) setDiff(d);
      })
      .catch((e) => {
        if (!cancelled) setError(e instanceof Error ? e.message : 'Failed to load diff');
      });
    return () => {
      cancelled = true;
    };
  }, [load]);

  return (
    <div style={overlayStyle} onClick={onClose}>
      <div
        className="max-h-[88vh] w-full max-w-4xl overflow-hidden rounded-2xl border border-border bg-surface p-6 shadow-2xl"
        onClick={(e) => e.stopPropagation()}
        style={{ display: 'flex', flexDirection: 'column' }}
      >
        <div className="mb-4 flex items-center justify-between">
          <h2 className="m-0 text-lg">Branch Diff</h2>
          <button
            className="cursor-pointer rounded border border-border bg-transparent px-2 py-0.5 text-muted hover:text-fg"
            onClick={onClose}
          >
            ✕
          </button>
        </div>

        {error && (
          <p className="rounded-lg border border-red/25 bg-red/8 px-3 py-2 font-mono text-[0.78rem] text-red">
            {error}
          </p>
        )}

        {!error && !diff && (
          <p className="font-mono text-sm text-muted">Loading diff…</p>
        )}

        {diff && (
          <div className="flex min-h-0 flex-col gap-4">
            {diff.branch && (
              <div className="font-mono text-[0.7rem] text-muted">
                ⎇ <span className="text-fg-dim">{diff.branch}</span> → main
              </div>
            )}

            <div>
              <h3 className="m-0 mb-1 text-[0.75rem] uppercase tracking-wider text-muted">
                Commits ({diff.commits.length})
              </h3>
              {diff.commits.length === 0 ? (
                <p className="m-0 font-mono text-[0.72rem] text-muted">No commits ahead — already merged or empty.</p>
              ) : (
                <ul className="m-0 list-none p-0 font-mono text-[0.72rem]">
                  {diff.commits.map((c) => (
                    <li key={c.sha} className="mb-0.5">
                      <span className="text-accent">{c.sha}</span>{' '}
                      <span className="text-fg-dim">{c.subject}</span>
                    </li>
                  ))}
                </ul>
              )}
            </div>

            {diff.stat && (
              <div>
                <h3 className="m-0 mb-1 text-[0.75rem] uppercase tracking-wider text-muted">Changes</h3>
                <pre className="m-0 overflow-x-auto rounded-lg border border-border bg-bg p-3 font-mono text-[0.68rem] leading-relaxed text-fg-dim">
                  {diff.stat}
                </pre>
              </div>
            )}

            <div className="min-h-0 flex-1">
              <h3 className="m-0 mb-1 text-[0.75rem] uppercase tracking-wider text-muted">
                Patch {diff.truncated && <span style={{ color: 'var(--accent)' }}>(truncated)</span>}
              </h3>
              <pre
                className="m-0 max-h-[44vh] overflow-auto rounded-lg border border-border bg-bg p-3 font-mono text-[0.66rem] leading-relaxed"
                style={{ whiteSpace: 'pre-wrap', wordBreak: 'break-word' }}
              >
                {diff.patch || '(no textual changes)'}
              </pre>
            </div>
          </div>
        )}
      </div>
    </div>
  );
}

const overlayStyle: React.CSSProperties = {
  position: 'fixed',
  inset: 0,
  background: 'rgba(0,0,0,0.6)',
  backdropFilter: 'blur(2px)',
  display: 'flex',
  alignItems: 'center',
  justifyContent: 'center',
  zIndex: 50,
  padding: 'var(--sp-4)',
};