import React, { useMemo, useState } from 'react';
import { Modal } from '../ui/Modal';
import { Avatar, Button, Field, IconButton, Segmented, inputClass } from '../ui/controls';
import { Icon } from '../ui/Icon';
import { useAuth } from '../../lib/auth';
import { projectsApi, type PotInput } from '../../lib/api';
import { addDays, addMonths, formatNumber, todayIso } from '../../lib/format';
import { useToast } from '../Toast';
import { CustomerForm } from '../customers/CustomerForm';
import type { Customer, DirectoryUser, Project, ProjectType } from '../../types';

export interface PotDraft {
  label: string;
  valid_from: string;
  valid_to: string;
  budget_amount: string;
  rate: string;
  budget_hours: string;
  budget_unit: 'hours' | 'days';
  notes: string;
}

export function emptyPot(start = todayIso(), label = 'Budget 1'): PotDraft {
  return { label, valid_from: start, valid_to: addDays(addMonths(start, 12), -1), budget_amount: '', rate: '', budget_hours: '', budget_unit: 'hours', notes: '' };
}

/** Deutsche und englische Schreibweise: "48.000,50", "48000.5", "110,5". */
export function num(value: string): number | null {
  const v = value.trim().replace(/\s|€/g, '');
  if (v === '') return null;
  if (v.includes(',')) return Number(v.replace(/\./g, '').replace(',', '.'));
  if (/^\d{1,3}(\.\d{3})+$/.test(v)) return Number(v.replace(/\./g, ''));
  return Number(v);
}

export function potPayload(draft: PotDraft, hoursPerDay: number): PotInput {
  const hours = num(draft.budget_hours);
  return {
    label: draft.label,
    valid_from: draft.valid_from,
    valid_to: draft.valid_to,
    budget_amount: num(draft.budget_amount),
    rate: num(draft.rate),
    budget_hours: hours == null ? null : draft.budget_unit === 'days' ? hours * hoursPerDay : hours,
    notes: draft.notes || null,
  };
}

/** Vorschau des buchbaren Volumens - gleiche Rechnung wie im Backend. */
export function potVolume(draft: PotDraft, type: ProjectType, unit: 'hour' | 'day', hoursPerDay: number) {
  const amount = num(draft.budget_amount);
  const rate = num(draft.rate);
  if (type === 'billable' && amount != null && rate) return (amount / rate) * (unit === 'day' ? hoursPerDay : 1);
  const hours = num(draft.budget_hours);
  if (hours == null) return null;
  return draft.budget_unit === 'days' ? hours * hoursPerDay : hours;
}

/** Felder eines Budgettopfs - im Projektformular und im Topfdialog. */
export const PotFields: React.FC<{
  draft: PotDraft;
  onChange: (draft: PotDraft) => void;
  type: ProjectType;
  unit: 'hour' | 'day';
}> = ({ draft, onChange, type, unit }) => {
  const { settings } = useAuth();
  const set = (patch: Partial<PotDraft>) => onChange({ ...draft, ...patch });
  const volume = potVolume(draft, type, unit, settings.hours_per_day);
  const unitLabel = unit === 'day' ? 'Tagessatz' : 'Stundensatz';
  return (
    <div className="space-y-3">
      <div className="grid gap-3 sm:grid-cols-3">
        <Field label="Bezeichnung" required className="sm:col-span-1">
          <input className={inputClass} value={draft.label} onChange={(e) => set({ label: e.target.value })} placeholder="z. B. Bestellung 4500030022" />
        </Field>
        <Field label="Laufzeit von" required>
          <input type="date" className={inputClass} value={draft.valid_from} onChange={(e) => set({ valid_from: e.target.value })} />
        </Field>
        <Field label="Laufzeit bis" required>
          <input type="date" className={inputClass} value={draft.valid_to} onChange={(e) => set({ valid_to: e.target.value })} />
        </Field>
      </div>
      <div className="grid gap-3 sm:grid-cols-3">
        {type !== 'non_billable' && (
          <Field label={type === 'fixed' ? 'Festpreis (€)' : 'Budget (€)'} required={type === 'fixed'}>
            <input inputMode="decimal" className={inputClass} value={draft.budget_amount} onChange={(e) => set({ budget_amount: e.target.value })} placeholder="z. B. 48000" />
          </Field>
        )}
        {type === 'billable' && (
          <Field label={`${unitLabel} (€)`} required>
            <input inputMode="decimal" className={inputClass} value={draft.rate} onChange={(e) => set({ rate: e.target.value })} placeholder={unit === 'day' ? 'z. B. 880' : 'z. B. 110'} />
          </Field>
        )}
        {(type !== 'billable' || !num(draft.budget_amount)) && (
          <Field label={type === 'fixed' ? 'Kontingent (optional)' : type === 'billable' ? 'oder Kontingent' : 'Kontingent (leer = unbegrenzt)'}>
            <div className="flex gap-2">
              <input inputMode="decimal" className={inputClass} value={draft.budget_hours} onChange={(e) => set({ budget_hours: e.target.value })} placeholder="–" />
              <select className={`${inputClass} w-24`} value={draft.budget_unit} onChange={(e) => set({ budget_unit: e.target.value as 'hours' | 'days' })}>
                <option value="hours">Std.</option>
                <option value="days">Tage</option>
              </select>
            </div>
          </Field>
        )}
      </div>
      <p className="flex items-center gap-2 rounded-xl bg-brand-50 px-3 py-2 text-xs font-semibold text-brand-800">
        <Icon name="pot" className="h-4 w-4 shrink-0" />
        {volume == null
          ? 'Unbegrenzt buchbar innerhalb der Laufzeit.'
          : `Buchbar: ${formatNumber(volume, 2)} Std. = ${formatNumber(volume / settings.hours_per_day, 1)} Tage – danach gesperrt, ebenso nach Ablauf.`}
        {type === 'fixed' && ' Virtueller Stundensatz = Festpreis ÷ gebuchte Stunden (intern).'}
      </p>
    </div>
  );
};

interface Props {
  project?: Project | null;
  customers: Customer[];
  users: DirectoryUser[];
  onClose: () => void;
  onSaved: (project: Project) => void;
  onCustomerCreated: (customer: Customer) => void;
}

export const ProjectForm: React.FC<Props> = ({ project, customers, users, onClose, onSaved, onCustomerCreated }) => {
  const { user, settings } = useAuth();
  const { addToast } = useToast();
  const editing = Boolean(project);
  const [customerId, setCustomerId] = useState<number | ''>(project?.customer_id ?? '');
  const [name, setName] = useState(project?.name ?? '');
  const [type, setType] = useState<ProjectType>(project?.type ?? 'billable');
  const [unit, setUnit] = useState<'hour' | 'day'>(project?.billing_unit ?? 'hour');
  // Nur fuer "Abruf": Satz am Projekt statt am Budgettopf.
  const [rate, setRate] = useState(project?.rate == null ? '' : String(project.rate).replace('.', ','));
  const [start, setStart] = useState(project?.start_date ?? todayIso());
  const [end, setEnd] = useState(project?.end_date ?? '');
  const isAdmin = user!.role === 'admin';
  const [ownerId, setOwnerId] = useState<number | ''>(project?.owner_id ?? (isAdmin ? '' : user!.id));
  const [tags, setTags] = useState<string[]>(project?.tags ?? []);
  const [tagText, setTagText] = useState('');
  const [notes, setNotes] = useState(project?.notes ?? '');
  const [members, setMembers] = useState<number[]>(project?.members.map((m) => m.id) ?? (isAdmin ? [] : [user!.id]));
  const [memberFilter, setMemberFilter] = useState('');
  const [tasks, setTasks] = useState<{ name: string; billable: boolean }[]>([{ name: '', billable: true }]);
  const [pots, setPots] = useState<PotDraft[]>([emptyPot()]);
  const [busy, setBusy] = useState(false);
  const [newCustomer, setNewCustomer] = useState(false);

  const customer = customers.find((c) => c.id === customerId);
  const codePreview = customer
    ? settings.project_code_pattern.replaceAll('{KUERZEL}', customer.short_name).replaceAll('{JAHR}', start.slice(0, 4)).replaceAll('{JJ}', start.slice(2, 4)).replaceAll('{NR}', '###')
    : '–';
  const namePreview = customer && name
    ? settings.project_name_pattern.replaceAll('{KUNDE}', customer.short_name === 'PERINCO' ? 'perinco' : customer.short_name).replaceAll('{KUNDENNAME}', customer.name).replaceAll('{PROJEKT}', name).replaceAll('{CODE}', project?.code ?? codePreview)
    : '';

  const activeUsers = useMemo(
    () => users.filter((u) => u.is_active && u.role !== 'admin' && (!memberFilter || u.name.toLowerCase().includes(memberFilter.toLowerCase()))),
    [users, memberFilter]
  );

  const addTag = () => {
    const parts = tagText.split(',').map((t) => t.trim()).filter(Boolean);
    if (parts.length) setTags([...new Set([...tags, ...parts])]);
    setTagText('');
  };

  const save = async () => {
    setBusy(true);
    try {
      const base = {
        customer_id: customerId,
        name,
        type,
        billing_unit: unit,
        rate: type === 'abruf' ? num(rate) : null,
        start_date: start,
        end_date: end || null,
        owner_id: ownerId || null,
        tags,
        notes,
        member_ids: members,
      };
      const saved = editing
        ? await projectsApi.update(project!.id, base)
        : await projectsApi.create({
            ...base,
            tasks: tasks.filter((t) => t.name.trim()),
            // Abruf kommt ohne Topf.
            pots: type === 'abruf' ? [] : pots.map((p) => potPayload(p, settings.hours_per_day)),
          });
      addToast(editing ? 'Projekt gespeichert.' : `Projekt ${saved.code} angelegt.`, 'success');
      onSaved(saved);
      onClose();
    } catch (err) {
      addToast(err instanceof Error ? err.message : 'Speichern fehlgeschlagen.', 'error');
    } finally {
      setBusy(false);
    }
  };

  return (
    <>
      <Modal
        size="xl"
        title={editing ? `Projekt bearbeiten` : 'Neues Projekt'}
        subtitle={editing ? `${project!.code} · ${project!.display_name}` : 'Projektcode wird automatisch vergeben'}
        onClose={onClose}
        footer={
          <div className="flex justify-end gap-2">
            <Button variant="secondary" onClick={onClose}>
              Abbrechen
            </Button>
            <Button icon="check" busy={busy} onClick={save}>
              {editing ? 'Speichern' : 'Projekt anlegen'}
            </Button>
          </div>
        }
      >
        <div className="space-y-6">
          <section className="grid gap-4 sm:grid-cols-2">
            <Field label="Kunde" required>
              <div className="flex gap-2">
                <select className={inputClass} value={customerId} onChange={(e) => setCustomerId(e.target.value ? Number(e.target.value) : '')}>
                  <option value="">Kunde wählen…</option>
                  {customers
                    .filter((c) => c.is_active || c.id === customerId)
                    .map((c) => (
                      <option key={c.id} value={c.id}>
                        {c.name} ({c.short_name})
                      </option>
                    ))}
                </select>
                <IconButton icon="plus" label="Neuen Kunden anlegen" type="button" onClick={() => setNewCustomer(true)} className="border border-ink-200" />
              </div>
            </Field>
            <Field label="Projektname" required hint={namePreview ? <>Anzeige: <b className="text-ink-700">{namePreview}</b></> : `Muster: ${settings.project_name_pattern}`}>
              <input className={inputClass} value={name} onChange={(e) => setName(e.target.value)} placeholder="z. B. PMO" />
            </Field>
            <Field label="Projektcode">
              <input className={`${inputClass} tabular`} value={project?.code ?? codePreview} disabled />
            </Field>
            <Field label="Projektverantwortlicher">
              <select className={inputClass} value={ownerId} onChange={(e) => setOwnerId(e.target.value ? Number(e.target.value) : '')}>
                <option value="">–</option>
                {users
                  .filter((u) => u.is_active && (u.role === 'lead' || u.role === 'management'))
                  .map((u) => (
                    <option key={u.id} value={u.id}>
                      {u.name}
                    </option>
                  ))}
              </select>
            </Field>
          </section>

          <section className="grid gap-4 sm:grid-cols-2">
            <div className="sm:col-span-2">
              <span className="field-label mb-1.5 block text-[11px] font-bold uppercase tracking-wider text-ink-500">Projekttyp</span>
              <div className="grid gap-2 sm:grid-cols-2 xl:grid-cols-4">
                {(
                  [
                    ['billable', 'Billable', 'Budgettopf mit Volumen und Laufzeit'],
                    ['abruf', 'Abruf', 'Nach Aufwand, ohne Budget – nur ein Satz'],
                    ['non_billable', 'Non-billable', 'z. B. perinco intern'],
                    ['fixed', 'Festpreis', 'Fixes Budget, virtueller Stundensatz'],
                  ] as const
                ).map(([value, label, hint]) => (
                  <button
                    key={value}
                    type="button"
                    onClick={() => setType(value)}
                    className={`rounded-xl border p-3 text-left transition ${type === value ? 'border-brand-400 bg-brand-50 shadow-card' : 'border-ink-200 hover:border-brand-200'}`}
                  >
                    <span className={`block text-sm font-extrabold ${type === value ? 'text-brand-700' : 'text-ink-800'}`}>{label}</span>
                    <span className="block text-[11px] text-ink-400">{hint}</span>
                  </button>
                ))}
              </div>
            </div>
            {(type === 'billable' || type === 'abruf') && (
              <Field label="Abrechnung">
                <Segmented value={unit} onChange={setUnit} options={[{ value: 'hour', label: 'Preis pro Stunde' }, { value: 'day', label: 'Preis pro Tag' }]} className="w-full" />
              </Field>
            )}
            {type === 'abruf' && (
              <Field
                label={unit === 'day' ? 'Tagessatz (€)' : 'Stundensatz (€)'}
                required
                hint="Abruf hat kein Budget: es wird gebucht, was anfällt, und mit diesem Satz bewertet."
              >
                <input inputMode="decimal" className={inputClass} value={rate} onChange={(e) => setRate(e.target.value)} placeholder={unit === 'day' ? 'z. B. 880' : 'z. B. 110'} />
              </Field>
            )}
            <div className="grid grid-cols-2 gap-3">
              <Field label="Startdatum" required>
                <input type="date" className={inputClass} value={start} onChange={(e) => setStart(e.target.value)} />
              </Field>
              <Field label="Enddatum">
                <input type="date" className={inputClass} value={end} onChange={(e) => setEnd(e.target.value)} />
              </Field>
            </div>
          </section>

          {!editing && type === 'abruf' && (
            <p className="flex items-start gap-2 rounded-xl bg-brand-50 px-3 py-2 text-xs font-semibold text-brand-800">
              <Icon name="pot" className="mt-0.5 h-4 w-4 shrink-0" />
              Kein Budgettopf: gebucht werden kann jederzeit innerhalb der Projektlaufzeit, der Umsatz ergibt sich aus den abrechenbaren Stunden mal dem Satz.
            </p>
          )}

          {!editing && type !== 'abruf' && (
            <section>
              <div className="mb-2 flex items-center justify-between">
                <h3 className="text-sm text-ink-900">Budgettöpfe</h3>
                <Button size="sm" variant="secondary" icon="plus" onClick={() => setPots([...pots, emptyPot(start, `Budget ${pots.length + 1}`)])}>
                  Topf hinzufügen
                </Button>
              </div>
              <div className="space-y-3">
                {pots.map((pot, i) => (
                  <div key={i} className="relative rounded-2xl border border-ink-200 p-4">
                    {pots.length > 1 && (
                      <IconButton icon="trash" tone="danger" label="Topf entfernen" className="absolute right-2 top-2" onClick={() => setPots(pots.filter((_, j) => j !== i))} />
                    )}
                    <PotFields draft={pot} type={type} unit={unit} onChange={(next) => setPots(pots.map((p, j) => (j === i ? next : p)))} />
                  </div>
                ))}
              </div>
            </section>
          )}

          {!editing && (
            <section>
              <h3 className="mb-2 text-sm text-ink-900">Tasks</h3>
              <div className="space-y-2">
                {tasks.map((task, i) => (
                  <div key={i} className="flex items-center gap-2">
                    <input
                      className={inputClass}
                      value={task.name}
                      placeholder="z. B. Administration Server"
                      onChange={(e) => {
                        const next = tasks.map((t, j) => (j === i ? { ...t, name: e.target.value } : t));
                        if (i === tasks.length - 1 && e.target.value) next.push({ name: '', billable: true });
                        setTasks(next);
                      }}
                    />
                    {type !== 'non_billable' && (
                      <label className="flex shrink-0 items-center gap-1.5 text-xs font-bold text-ink-500">
                        <input type="checkbox" checked={task.billable} onChange={(e) => setTasks(tasks.map((t, j) => (j === i ? { ...t, billable: e.target.checked } : t)))} />
                        billable
                      </label>
                    )}
                  </div>
                ))}
              </div>
            </section>
          )}

          <section>
            <div className="mb-2 flex flex-wrap items-center justify-between gap-2">
              <h3 className="text-sm text-ink-900">
                Zugewiesene Mitarbeiter <span className="text-ink-400">({members.length})</span>
              </h3>
              <input className={`${inputClass} w-48 py-1.5`} placeholder="Suchen…" value={memberFilter} onChange={(e) => setMemberFilter(e.target.value)} />
            </div>
            <div className="scrollbar-slim grid max-h-56 gap-1.5 overflow-y-auto sm:grid-cols-2 lg:grid-cols-3">
              {activeUsers.map((u) => {
                const checked = members.includes(u.id);
                return (
                  <label key={u.id} className={`flex cursor-pointer items-center gap-2 rounded-xl border px-2.5 py-2 transition ${checked ? 'border-brand-300 bg-brand-50' : 'border-ink-200 hover:bg-ink-50'}`}>
                    <input type="checkbox" className="accent-[var(--color-brand-500)]" checked={checked} onChange={() => setMembers(checked ? members.filter((id) => id !== u.id) : [...members, u.id])} />
                    <Avatar id={u.id} name={u.name} color={u.color} size={24} external={u.is_external} />
                    <span className="min-w-0 truncate text-xs font-bold text-ink-700">{u.name}</span>
                  </label>
                );
              })}
            </div>
          </section>

          <section className="grid gap-4 sm:grid-cols-2">
            <Field label="Tags">
              <div className="flex flex-wrap items-center gap-1.5 rounded-xl border border-ink-200 px-2 py-1.5">
                {tags.map((t) => (
                  <span key={t} className="flex items-center gap-1 rounded-full bg-ink-100 px-2 py-0.5 text-xs font-bold text-ink-600">
                    {t}
                    <button type="button" onClick={() => setTags(tags.filter((x) => x !== t))} aria-label={`${t} entfernen`}>
                      <Icon name="close" className="h-3 w-3" />
                    </button>
                  </span>
                ))}
                <input
                  className="min-w-[80px] flex-1 bg-transparent px-1 py-1 text-sm outline-none"
                  value={tagText}
                  placeholder="Tag + Enter"
                  onChange={(e) => setTagText(e.target.value)}
                  onBlur={addTag}
                  onKeyDown={(e) => {
                    if (e.key === 'Enter' || e.key === ',') {
                      e.preventDefault();
                      addTag();
                    }
                  }}
                />
              </div>
            </Field>
            <Field label="Notizen">
              <textarea className={`${inputClass} h-24 resize-y`} value={notes} onChange={(e) => setNotes(e.target.value)} placeholder="z. B. Rechnungen nur mit Belegnummer…" />
            </Field>
          </section>
        </div>
      </Modal>
      {newCustomer && (
        <CustomerForm
          onClose={() => setNewCustomer(false)}
          onSaved={(c) => {
            onCustomerCreated(c);
            setCustomerId(c.id);
          }}
        />
      )}
    </>
  );
};