'use client';

import { useCallback, useEffect, useState } from 'react';
import { clearStoredSession, sessionHeaders, storedSession, storeSession } from '../lib/authClient';

// v0.71.0 — content of the Admin modal (opened by the top-bar "Admin" button). Three views:
// login form (no valid session), a "not an admin" notice, or the generic whole-database CRUD
// grid behind /api/admin/*. This is a dev tool surface — plain and functional on purpose.

interface Me {
  username: string;
  admin: boolean;
}

interface RowsData {
  columns: string[];
  rows: Array<Record<string, unknown>>;
}

export default function AdminPanel({ onLogout }: { onLogout?: () => void }) {
  const [session, setSession] = useState<string | null>(null);
  const [me, setMe] = useState<Me | null>(null); // null while checking /api/me on mount
  const [checking, setChecking] = useState(true);

  // Login form state.
  const [username, setUsername] = useState('');
  const [password, setPassword] = useState('');
  const [loginError, setLoginError] = useState<string | null>(null);

  // Admin grid state.
  const [tables, setTables] = useState<string[]>([]);
  const [table, setTable] = useState<string | null>(null);
  const [rowsData, setRowsData] = useState<RowsData | null>(null);
  const [edits, setEdits] = useState<Record<string, string>>({}); // key `${rowIdx}:${col}`
  const [newRow, setNewRow] = useState(false);
  const [busy, setBusy] = useState(false);
  const [error, setError] = useState<string | null>(null);

  const authHeaders = useCallback((s: string) => sessionHeaders(s), []);

  // On mount: a stored session decides between the grid and the login form.
  useEffect(() => {
    let cancelled = false;
    const stored = storedSession();
    if (!stored) {
      setChecking(false);
      return;
    }
    fetch('/api/me', { headers: authHeaders(stored) })
      .then(async (res) => {
        if (!res.ok || cancelled) {
          clearStoredSession();
          setSession(null);
          return;
        }
        const body = (await res.json()) as Me;
        setSession(stored);
        setMe(body);
      })
      .catch(() => {
        if (!cancelled) {
          clearStoredSession();
          setSession(null);
        }
      })
      .finally(() => {
        if (!cancelled) setChecking(false);
      });
    return () => {
      cancelled = true;
    };
  }, [authHeaders]);

  const loadTables = useCallback(async (s: string) => {
    const res = await fetch('/api/admin/tables', { headers: authHeaders(s) });
    if (!res.ok) throw new Error((await res.json().catch(() => null))?.error ?? `HTTP ${res.status}`);
    setTables(((await res.json()) as Array<{ name: string }>).map((t) => t.name));
  }, [authHeaders]);

  const loadRows = useCallback(
    async (s: string, name: string) => {
      const res = await fetch(`/api/admin/tables/${encodeURIComponent(name)}/rows?limit=500`, { headers: authHeaders(s) });
      if (!res.ok) throw new Error((await res.json().catch(() => null))?.error ?? `HTTP ${res.status}`);
      setRowsData(await res.json());
    },
    [authHeaders],
  );

  // Enter the grid once /api/me confirms an admin.
  useEffect(() => {
    if (!session || !me?.admin) return;
    let cancelled = false;
    (async () => {
      try {
        await loadTables(session);
        if (!cancelled) setBusy(false);
      } catch (err) {
        if (!cancelled) setError(err instanceof Error ? err.message : String(err));
      } finally {
        if (!cancelled) setBusy(false);
      }
    })();
    return () => {
      cancelled = true;
    };
  }, [session, me, loadTables]);

  const openTable = async (name: string) => {
    if (!session) return;
    setBusy(true);
    setError(null);
    try {
      await loadRows(session, name);
      setTable(name);
      setEdits({});
      setNewRow(false);
    } catch (err) {
      setError(err instanceof Error ? err.message : String(err));
    } finally {
      setBusy(false);
    }
  };

  const refresh = async () => {
    if (!session || !table) return;
    setBusy(true);
    setError(null);
    try {
      await loadRows(session, table);
      setEdits({});
      setNewRow(false);
    } catch (err) {
      setError(err instanceof Error ? err.message : String(err));
    } finally {
      setBusy(false);
    }
  };

  const login = async () => {
    if (!username || !password) return;
    setLoginError(null);
    const res = await fetch('/api/login', {
      method: 'POST',
      headers: { 'content-type': 'application/json' },
      body: JSON.stringify({ username, password }),
    });
    if (!res.ok) {
      setLoginError((await res.json().catch(() => null))?.error ?? `HTTP ${res.status}`);
      return;
    }
    const body = (await res.json()) as { sessionId: string; user: Me };
    storeSession(body.sessionId);
    setSession(body.sessionId);
    setMe(body.user);
    setUsername('');
    setPassword('');
  };

  const logout = async () => {
    if (session) await fetch('/api/logout', { method: 'POST', headers: authHeaders(session) }).catch(() => undefined);
    clearStoredSession();
    onLogout?.(); // v1.1.0 (ISS-107): session gone → shell drops back to the sign-in screen
    setSession(null);
    setMe(null);
    setTable(null);
    setRowsData(null);
    setTables([]);
    setError(null);
  };

  if (checking) return <div className="admin-panel">loading…</div>;

  // No valid session → login form.
  if (!session || !me) {
    return (
      <form
        className="admin-panel admin-login"
        onSubmit={(e) => {
          e.preventDefault();
          void login();
        }}
      >
        <label>
          Username
          <input data-testid="admin-username" value={username} onChange={(e) => setUsername(e.target.value)} autoComplete="username" />
        </label>
        <label>
          Password
          <input
            data-testid="admin-password"
            type="password"
            value={password}
            onChange={(e) => setPassword(e.target.value)}
            autoComplete="current-password"
          />
        </label>
        {loginError && (
          <div data-testid="admin-error" className="admin-error">
            {loginError}
          </div>
        )}
        <button type="submit" data-testid="admin-login-submit" className="pane-btn">
          Log in
        </button>
      </form>
    );
  }

  // Authenticated but not an admin.
  if (!me.admin) {
    return (
      <div className="admin-panel">
        <p data-testid="admin-not-admin" className="admin-message">
          Logged in as <strong>{me.username}</strong> — this account is not an admin.
        </p>
        <button type="button" data-testid="admin-logout" className="pane-btn" onClick={() => void logout()}>
          Log out
        </button>
      </div>
    );
  }

  const columns = rowsData?.columns ?? [];
  // Displayed grid: server rows plus one trailing empty row when "+ Add row" is active.
  const rowCount = (rowsData?.rows.length ?? 0) + (newRow ? 1 : 0);
  const cellValue = (rowIdx: number, col: string): string => {
    if (col === '__rowid') return String(rowsData?.rows[rowIdx]?.[col] ?? '');
    const key = `${rowIdx}:${col}`;
    if (key in edits) return edits[key];
    const raw = rowsData?.rows[rowIdx]?.[col];
    return raw === null || raw === undefined ? '' : String(raw);
  };

  const saveRow = async (rowIdx: number) => {
    if (!session || !table || !rowsData) return;
    setBusy(true);
    setError(null);
    try {
      if (newRow && rowIdx === rowsData.rows.length) {
        // New row → POST the non-empty cells.
        const values: Record<string, string> = {};
        for (const col of columns) {
          if (col === '__rowid') continue;
          const v = cellValue(rowIdx, col);
          if (v !== '') values[col] = v;
        }
        const res = await fetch(`/api/admin/tables/${encodeURIComponent(table)}/rows`, {
          method: 'POST',
          headers: { 'content-type': 'application/json', ...authHeaders(session) },
          body: JSON.stringify({ values }),
        });
        if (!res.ok) throw new Error((await res.json().catch(() => null))?.error ?? `HTTP ${res.status}`);
      } else {
        // Existing row → PUT only the changed cells (cleared cell = NULL).
        const values: Record<string, string | null> = {};
        for (const col of columns) {
          if (col === '__rowid') continue;
          const original = rowsData.rows[rowIdx]?.[col];
          const origStr = original === null || original === undefined ? '' : String(original);
          const v = cellValue(rowIdx, col);
          if (v !== origStr) values[col] = v === '' ? null : v;
        }
        if (Object.keys(values).length === 0) return; // nothing changed
        const res = await fetch(`/api/admin/tables/${encodeURIComponent(table)}/rows`, {
          method: 'PUT',
          headers: { 'content-type': 'application/json', ...authHeaders(session) },
          body: JSON.stringify({ rowid: rowsData.rows[rowIdx]?.__rowid, values }),
        });
        if (!res.ok) throw new Error((await res.json().catch(() => null))?.error ?? `HTTP ${res.status}`);
      }
      await loadRows(session, table); // re-fetch so the grid shows server state (persistence check)
      setEdits({});
      setNewRow(false);
    } catch (err) {
      setError(err instanceof Error ? err.message : String(err));
    } finally {
      setBusy(false);
    }
  };

  const deleteRow = async (rowIdx: number) => {
    if (!session || !table || !rowsData?.rows[rowIdx]) return;
    setBusy(true);
    setError(null);
    try {
      const rowid = rowsData.rows[rowIdx]?.__rowid;
      const res = await fetch(
        `/api/admin/tables/${encodeURIComponent(table)}/rows?rowid=${encodeURIComponent(String(rowid))}`,
        { method: 'DELETE', headers: authHeaders(session) },
      );
      if (!res.ok) throw new Error((await res.json().catch(() => null))?.error ?? `HTTP ${res.status}`);
      await loadRows(session, table);
      setEdits({});
    } catch (err) {
      setError(err instanceof Error ? err.message : String(err));
    } finally {
      setBusy(false);
    }
  };

  return (
    <div className="admin-panel">
      <div className="admin-toolbar">
        <span data-testid="admin-user" className="admin-message">
          {me.username} (admin)
        </span>
        <button type="button" data-testid="admin-logout" className="pane-btn" onClick={() => void logout()}>
          Log out
        </button>
      </div>

      {!table && (
        <>
          <p className="admin-message">Pick a table:</p>
          <div data-testid="admin-tables" className="admin-table-list">
            {tables.map((t) => (
              <button key={t} type="button" data-testid={`admin-table-${t}`} className="pane-btn" onClick={() => void openTable(t)}>
                {t}
              </button>
            ))}
          </div>
        </>
      )}

      {table && rowsData && (
        <>
          <div className="admin-toolbar">
            <strong data-testid="admin-current-table">{table}</strong>
            <button type="button" data-testid="admin-back" className="pane-btn" onClick={() => setTable(null)}>
              ← tables
            </button>
            <button type="button" data-testid="admin-refresh" className="pane-btn" disabled={busy} onClick={() => void refresh()}>
              Refresh
            </button>
            <button
              type="button"
              data-testid="admin-add-row"
              className="pane-btn"
              disabled={busy || newRow}
              onClick={() => setNewRow(true)}
            >
              + Add row
            </button>
          </div>

          <div className="admin-rows-wrap">
            <table data-testid="admin-rows" className="admin-rows">
              <thead>
                <tr>
                  {columns.map((c) => (
                    <th key={c}>{c}</th>
                  ))}
                  <th />
                </tr>
              </thead>
              <tbody>
                {Array.from({ length: rowCount }, (_, i) => (
                  <tr key={i}>
                    {columns.map((c) => (
                      <td key={c}>
                        <input
                          data-testid={`admin-cell-${i}-${c}`}
                          className="admin-cell"
                          value={cellValue(i, c)}
                          disabled={busy || c === '__rowid'}
                          onChange={(e) => setEdits((prev) => ({ ...prev, [`${i}:${c}`]: e.target.value }))}
                        />
                      </td>
                    ))}
                    <td className="admin-row-actions">
                      <button type="button" data-testid={`admin-save-${i}`} className="pane-btn" disabled={busy} onClick={() => void saveRow(i)}>
                        Save
                      </button>{' '}
                      {!(newRow && i === rowsData.rows.length) && (
                        <>
                          <button
                            type="button"
                            data-testid={`admin-delete-${i}`}
                            className="pane-btn"
                            disabled={busy}
                            onClick={() => void deleteRow(i)}
                          >
                            Delete
                          </button>{' '}
                        </>
                      )}
                    </td>
                  </tr>
                ))}
              </tbody>
            </table>
          </div>
        </>
      )}

      {error && (
        <div data-testid="admin-error" className="admin-error">
          {error}
        </div>
      )}
    </div>
  );
}