import { useCallback, useEffect, useRef, useState } from 'react';
import { ArrowUpFromLine, Check, CircleCheck, CircleDashed, Database, DatabaseBackup, Loader2, Plus } from 'lucide-react';
import { useClient } from 'hooks/useClient';
import { Button } from '@/components/ui/button';
import { Input } from '@/components/ui/input';
import { readableError } from './errors';
import { Block } from './Block';
import { useFlash } from './useFlash';

/**
 * Where the fofos site's own data lives — two databases, named here.
 *
 * ── ONE button ──
 *
 * It shipped with two — Save, then Create — on the reasoning that naming and creating are different
 * decisions. They are not, from the outside: you type two names because you want two databases. Worse,
 * Create keyed off the SAVED names, so on a fresh screen with both fields filled it did not appear at
 * all, and the hint explaining why was behind the same condition. Two filled fields, one Save button,
 * and no way to tell what came next.
 *
 * So one button that records the names and creates whatever is not there, labelled with whichever of
 * those it is actually about to do. Recording the name you just used to make a database is not a side
 * effect worth a second click.
 *
 * ── It reports what is THERE, against what is TYPED ──
 *
 * The tick beside each field asks `pg_database` whether a database of that name exists, and it asks
 * about the text in the box rather than the text that was last saved. That is the question somebody
 * typing a name actually has, and answering it about a different name would be worse than silence.
 */

type Named = { name: string | null; exists: boolean | null; tables: number | null };
type Status = { production: Named; development: Named; available: string[] };

export const DatabaseBlock = () => {
  const client = useClient();
  const clientRef = useRef(client);
  clientRef.current = client;

  const [status, setStatus] = useState<Status | null>(null);
  const [production, setProduction] = useState('');
  const [development, setDevelopment] = useState('');
  const [busy, setBusy] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const [flashing, flash] = useFlash();

  const load = useCallback(async () => {
    try {
      const current = await clientRef.current.get<Status>('/fofos-admin/_config/databases');
      setStatus(current);
      // Only seed the fields from the server when they are untouched, so a reload landing mid-typing
      // cannot replace what somebody is in the middle of writing.
      setProduction((typed) => typed || (current.production.name ?? ''));
      setDevelopment((typed) => typed || (current.development.name ?? ''));
    } catch {
      setStatus(null);
    }
  }, []);

  useEffect(() => {
    void load();
  }, [load]);

  const [output, setOutput] = useState<string | null>(null);

  /**
   * Push the site's schema into one of the two.
   *
   * Runs the WEBSITE's own `db:push` — the schema and the drizzle version belong to that repository,
   * and a plugin that reimplemented either would be a second definition of the site's database going
   * stale on its own schedule.
   */
  const push = async (target: 'production' | 'development') => {
    setBusy(true);
    setError(null);
    setOutput(null);
    try {
      const result = await clientRef.current.post<{ ok: boolean; output: string; status: Status }>(
        `/fofos-admin/_config/databases/${target}/push-schema`,
        {},
      );
      setStatus(result.status);
      setOutput(result.output);
    } catch (failure) {
      setError(readableError(failure));
    } finally {
      setBusy(false);
    }
  };

  /** Records the names and creates whichever is missing. The server does both, in that order. */
  const apply = async () => {
    setBusy(true);
    setError(null);
    try {
      const result = await clientRef.current.post<{ created: string[]; status: Status }>(
        '/fofos-admin/_config/databases/create',
        { production, development },
      );
      setStatus(result.status);
      flash();
    } catch (failure) {
      setError(readableError(failure));
    } finally {
      setBusy(false);
    }
  };

  const field = (label: string, hint: string, value: string, onChange: (next: string) => void) => {
    // Against the typed text and the real list from `pg_database`. Nothing to say about an empty box.
    const typed = value.trim();
    const exists = typed ? (status?.available.includes(typed) ?? false) : null;
    const Icon = exists ? CircleCheck : CircleDashed;

    return (
      <div className="space-y-1">
        <div className="flex items-baseline gap-2">
          <label className="text-xs font-medium">{label}</label>
          <span className="text-xs text-muted-foreground/70">{hint}</span>
        </div>
        <div className="flex items-center gap-2">
          <Input
            value={value}
            onChange={(event) => onChange(event.target.value)}
            placeholder={label === 'Production' ? 'fofos_website' : 'fofos_website_dev'}
            className="w-full font-mono text-xs"
            autoComplete="off"
            spellCheck={false}
          />
          <span className="flex w-24 shrink-0 items-center gap-1 text-xs text-muted-foreground">
            {exists === null ? null : (
              <>
                <Icon className={`size-3.5 ${exists ? 'text-success' : ''}`} />
                {exists ? 'exists' : 'not yet'}
              </>
            )}
          </span>
        </div>
      </div>
    );
  };

  const dirty =
    production.trim() !== (status?.production.name ?? '') || development.trim() !== (status?.development.name ?? '');

  // Typed, non-empty, and not on the instance. What the one button is about to make.
  const missing = [production.trim(), development.trim()].filter(
    (name) => name && !(status?.available.includes(name) ?? false),
  );

  const label = missing.length ? `Create ${missing.length === 1 ? missing[0] : 'databases'}` : 'Save names';

  /*
    Settled: both named, both there. The fields have nothing left to do — a text box invites an edit
    nobody is here to make, and the two things somebody DOES want at this point are per-database
    actions rather than a form.
  */
  const settled = Boolean(
    status?.production.exists && status?.development.exists && !dirty && production.trim() && development.trim(),
  );

  const row = (label: string, target: 'production' | 'development', state: Named) => {
    // "Schema pushed" is simply: something is in it. See the note on `tables`.
    const pushed = (state.tables ?? 0) > 0;

    return (
      <div className="flex items-center gap-3">
        <div className="min-w-0 flex-1">
          <p className="text-xs text-muted-foreground">{label}</p>
          <p className="truncate font-mono text-xs">{state.name}</p>
        </div>

        <span className="shrink-0 text-xs text-muted-foreground/70">
          {state.tables === null ? '' : pushed ? `${state.tables} tables` : 'empty'}
        </span>

        <div className="flex shrink-0 gap-2">
          <Button variant="outline" size="sm" onClick={() => void push(target)} disabled={busy}>
            {busy ? <Loader2 className="size-3.5 animate-spin" /> : <ArrowUpFromLine className="size-3.5" />}
            Push schema
          </Button>

          {/* Nothing to restore INTO until there are tables to restore into — a data-only load against
              an empty database fails on every insert, and the failure would read as a bad backup. */}
          <Button variant="outline" size="sm" disabled title={pushed ? undefined : 'Push the schema first'}>
            <DatabaseBackup className="size-3.5" />
            Restore from backup
          </Button>
        </div>
      </div>
    );
  };

  return (
    <Block
      icon={Database}
      title="Database"
      hint="Where the fofos site's own data lives — on Officer's own Postgres."
      status={
        flashing ? (
          <span className="flex items-center gap-1 text-xs text-success">
            <Check className="size-3.5" />
            Saved
          </span>
        ) : undefined
      }
    >
      {!status ? null : settled ? (
        <>
          {row('Production', 'production', status.production)}
          {row('Development', 'development', status.development)}
          {error && <p className="text-xs text-destructive">{error}</p>}
          {output && (
            <pre className="max-h-48 overflow-auto rounded bg-black p-3 font-mono text-[11px] whitespace-pre-wrap text-white/90">
              {output}
            </pre>
          )}
        </>
      ) : (
        <>
          {field('Production', 'what the live site reads', production, setProduction)}
          {field('Development', 'what you work against', development, setDevelopment)}

          {error && <p className="text-xs text-destructive">{error}</p>}

          <div className="flex justify-end border-t border-border pt-3">
            {/* Nothing missing and nothing changed means there is genuinely nothing to press. */}
            <Button
              size="sm"
              onClick={() => void apply()}
              disabled={busy || (!missing.length && !dirty) || !production.trim() || !development.trim()}
            >
              {busy ? (
                <Loader2 className="size-3.5 animate-spin" />
              ) : missing.length ? (
                <Plus className="size-3.5" />
              ) : (
                <Check className="size-3.5" />
              )}
              {label}
            </Button>
          </div>
        </>
      )}
    </Block>
  );
};