import * as React from 'react';
import { Check } from 'lucide-react';
import { cn } from '@/lib/utils';
import { Button, Modal, SearchInput } from '@/components/ds';
import { allSkills, skillsWithFacet } from '@/lib/skills/registry';
import { surfaceFor } from '@/lib/skills/surfaces';

/**
 * Attaching skills to an agent.
 *
 * Reads **the one skill registry** — the same `allSkills` the Skills page and
 * Owliver itself read. There is deliberately no separate list for agents: a
 * second one would drift, and an agent would end up offering a skill the
 * runtime does not have.
 *
 * Categories are derived rather than written down. A skill's own `category`
 * field when it declares one, and the pages it attaches to otherwise, so a
 * filter can never offer a grouping that matches nothing — and a skill added
 * tomorrow appears under its own category without this file being edited.
 */

const ALL = 'all';

/** The groupings the registry actually contains, in a stable order. */
function categoriesFor(skills) {
  const named = new Set();
  for (const skill of skills) {
    if (skill.category) named.add(skill.category);
  }
  return [ALL, ...[...named].sort()];
}

/** What this skill contributes, in the terms the reader is choosing between. */
function skillSummary(skill) {
  const pages = skill.pages.map((p) => surfaceFor(p)?.label || p);
  const capabilities = skill.owliver?.capabilities || [];
  return [
    pages.length ? pages.join(', ') : 'No pages',
    capabilities.length
      ? `${capabilities.length} capabilit${capabilities.length === 1 ? 'y' : 'ies'}`
      : (skill.actions || []).length ? `${skill.actions.length} action${skill.actions.length === 1 ? '' : 's'}` : null,
  ].filter(Boolean).join(' · ');
}

/** @param {any} props */
export function AddSkillsModal({ open, onOpenChange, attached = [], customSkills = [], onAdd }) {
  const [query, setQuery] = React.useState('');
  const [category, setCategory] = React.useState(ALL);
  const [picked, setPicked] = React.useState([]);

  /* A fresh sheet each time, so a previous selection is not still ticked. */
  React.useEffect(() => {
    if (open) { setQuery(''); setCategory(ALL); setPicked([]); }
  }, [open]);

  /* Owliver skills only. A workforce training path is something a person
     learns, not something an agent can be asked to do, and offering one here
     would promise behaviour that does not exist. */
  const available = React.useMemo(
    () => skillsWithFacet(allSkills(customSkills), 'owliver')
      .filter((s) => s.status === 'active' && !attached.includes(s.id)),
    [customSkills, attached]
  );

  const categories = React.useMemo(() => categoriesFor(available), [available]);

  const visible = React.useMemo(() => {
    const q = query.trim().toLowerCase();
    return available
      .filter((s) => category === ALL || s.category === category)
      .filter((s) => !q
        || s.name.toLowerCase().includes(q)
        || s.description.toLowerCase().includes(q)
        || s.id.includes(q));
  }, [available, category, query]);

  const toggle = (id) =>
    setPicked((current) => (current.includes(id)
      ? current.filter((x) => x !== id)
      : [...current, id]));

  return (
    <Modal
      open={open}
      onOpenChange={onOpenChange}
      title="Add skills"
      description="Select skills to extend what this agent can do. A skill still only answers on the pages it names."
      size="lg"
      footer={
        <>
          <p className="mr-auto text-body-sm text-ink-3">
            {picked.length
              ? `${picked.length} skill${picked.length === 1 ? '' : 's'} selected`
              : 'Nothing selected yet'}
          </p>
          <Button variant="outline" onClick={() => onOpenChange(false)}>Cancel</Button>
          <Button disabled={!picked.length} onClick={() => { onAdd(picked); onOpenChange(false); }}>
            Add
          </Button>
        </>
      }
    >
      <div className="space-y-3">
        <SearchInput value={query} onChange={setQuery} placeholder="Search skills..." debounce={0} />

        {categories.length > 1 && (
          <div className="flex flex-wrap gap-1.5">
            {categories.map((id) => (
              <button
                key={id}
                type="button"
                onClick={() => setCategory(id)}
                className={cn(
                  `rounded-full border px-2.5 py-1 text-caption font-medium capitalize transition-colors
                   focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-krow-blue/50`,
                  category === id
                    ? 'border-krow-blue/40 bg-krow-blue-tint text-krow-blue'
                    : 'border-border bg-surface text-ink-3 hover:border-krow-blue/30 hover:text-ink-2'
                )}
              >
                {id === ALL ? 'All skills' : id}
              </button>
            ))}
          </div>
        )}

        <div className="max-h-[22rem] space-y-1.5 overflow-y-auto pr-0.5">
          {visible.map((skill) => {
            const chosen = picked.includes(skill.id);
            return (
              <button
                key={skill.id}
                type="button"
                onClick={() => toggle(skill.id)}
                aria-pressed={chosen}
                className={cn(
                  `flex w-full items-start gap-2.5 rounded-xl border px-3 py-2.5 text-left transition-colors
                   focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-krow-blue/50`,
                  chosen
                    ? 'border-krow-blue/50 bg-krow-blue-tint/50'
                    : 'border-border bg-surface hover:border-krow-blue/30 hover:bg-surface-subtle'
                )}
              >
                <span
                  className={cn(
                    'mt-0.5 flex h-4 w-4 shrink-0 items-center justify-center rounded border',
                    chosen ? 'border-krow-blue bg-krow-blue text-white' : 'border-border bg-surface'
                  )}
                  aria-hidden="true"
                >
                  {chosen && <Check className="h-3 w-3" />}
                </span>

                <span className="min-w-0 flex-1">
                  <span className="block truncate text-body-sm font-medium text-ink-1">{skill.name}</span>
                  {skill.description && (
                    <span className="mt-0.5 block text-caption leading-snug text-ink-3">
                      {skill.description}
                    </span>
                  )}
                  <span className="mt-1 block truncate text-[10px] text-ink-4">{skillSummary(skill)}</span>
                </span>
              </button>
            );
          })}

          {!visible.length && (
            <p className="px-1 py-6 text-center text-body-sm text-ink-3">
              {available.length
                ? 'No skills match that.'
                : 'Every available skill is already attached to this agent.'}
            </p>
          )}
        </div>
      </div>
    </Modal>
  );
}

export default AddSkillsModal;