import { useState } from 'react';
import { Link } from '@tanstack/react-router';
import type { Character } from '@/lib/schemas';
import type { AbilityKey, CharacterRulesInput, ProficiencyRank, SystemId } from '@/lib/rules';
import { getSystem, ABILITY_ABBR } from '@/lib/rules';
import { charactersRepo } from '@/lib/db/repositories';
import { PF2E_SAVES } from '@/lib/rules/pf2e/skills';
import { useDebouncedCallback } from '@/lib/useDebouncedCallback';
import { rollCheck } from '@/lib/useRoll';
import { Page } from '@/components/ui/Page';
import { Button } from '@/components/ui/Button';
import { Input, Select } from '@/components/ui/Input';
import { NumberField } from '@/components/ui/NumberField';
import { formatModifier } from '@/lib/format';
import { InventorySection } from './sheet/InventorySection';
import { AttacksSection } from './sheet/AttacksSection';
import { ResourcesSection } from './sheet/ResourcesSection';
import { SpellcastingSection } from './sheet/SpellcastingSection';
import { DefensesSection } from './sheet/DefensesSection';

const ABILITIES: AbilityKey[] = ['str', 'dex', 'con', 'int', 'wis', 'cha'];

const RANKS_5E: ProficiencyRank[] = ['untrained', 'trained', 'expert'];
const RANKS_PF2E: ProficiencyRank[] = ['untrained', 'trained', 'expert', 'master', 'legendary'];
const RANK_LABEL: Record<ProficiencyRank, string> = {
  untrained: 'Untrained',
  trained: 'Trained',
  expert: 'Expert',
  master: 'Master',
  legendary: 'Legendary',
};

export function CharacterSheet({ character }: { character: Character }) {
  // Local editable copy; write-through to the DB on change (debounced + flush on unmount).
  const [c, setC] = useState<Character>(character);
  const save = useDebouncedCallback((next: Character) => {
    // Persist everything except identity/timestamps (update() stamps updatedAt).
    const { id, campaignId: _campaignId, createdAt: _createdAt, updatedAt: _updatedAt, ...rest } = next;
    void charactersRepo.update(id, rest);
  }, 350);

  const update = (patch: Partial<Character>) => {
    setC((prev) => {
      const next = { ...prev, ...patch };
      save(next);
      return next;
    });
  };

  const sys = getSystem(c.system);
  const rulesInput: CharacterRulesInput = {
    level: c.level,
    abilities: c.abilities,
    skillRanks: c.skillRanks as Record<string, ProficiencyRank>,
    saveRanks: c.saveRanks as Partial<Record<AbilityKey, ProficiencyRank>>,
    armorBonus: c.armorBonus,
    perceptionRank: c.perceptionRank,
    ...(c.spellcastingRank ? { spellcastingRank: c.spellcastingRank } : {}),
  };

  const ac = sys.baseArmorClass(rulesInput);
  const initiative = sys.initiativeModifier(rulesInput);
  const skills = sys.skillModifiers(rulesInput);
  const saves = sys.saveModifiers(rulesInput);
  const profLabel = c.system === '5e' ? `+${sys.proficiencyValue(c.level, 'trained')} prof` : `level ${c.level}`;
  const ranks = c.system === 'pf2e' ? RANKS_PF2E : RANKS_5E;

  return (
    <Page>
      <div className="mb-4">
        <Link to="/characters" className="text-sm text-muted hover:text-ink">
          ← Back to characters
        </Link>
      </div>

      {/* Header */}
      <div className="mb-6 flex flex-wrap items-center gap-3">
        <Input
          className="max-w-xs font-display text-xl font-bold"
          value={c.name}
          aria-label="Character name"
          onChange={(e) => update({ name: e.target.value })}
        />
        <span className="rounded-full bg-elevated px-2 py-0.5 text-xs uppercase tracking-wide text-muted">
          {c.kind === 'pc' ? 'PC' : 'NPC'} · {sys.label}
        </span>
        <div className="ml-auto text-sm text-muted">{profLabel}</div>
      </div>

      <div className="mb-6 grid gap-3 sm:grid-cols-2 lg:grid-cols-4">
        <Labeled label={c.system === 'pf2e' ? 'Ancestry' : 'Race'}>
          <Input value={c.ancestry} onChange={(e) => update({ ancestry: e.target.value })} />
        </Labeled>
        <Labeled label="Class">
          <Input value={c.className} onChange={(e) => update({ className: e.target.value })} />
        </Labeled>
        <Labeled label="Level">
          <NumberField value={c.level} min={1} max={20} onChange={(level) => update({ level })} />
        </Labeled>
        <Labeled label="Speed">
          <NumberField value={c.speed} min={0} onChange={(speed) => update({ speed })} />
        </Labeled>
      </div>

      {/* Vital stats */}
      <div className="mb-6 grid gap-3 sm:grid-cols-3">
        <StatCard label="Armor Class" value={ac} hint={`10 + DEX${c.armorBonus ? ` + ${c.armorBonus}` : ''}`}>
          <div className="mt-2 flex items-center justify-center gap-2 text-xs text-muted">
            <span>Armor/shield bonus</span>
            <NumberField className="w-16" value={c.armorBonus} onChange={(armorBonus) => update({ armorBonus })} aria-label="Armor bonus" />
          </div>
        </StatCard>

        <StatCard label="Initiative" value={formatModifier(initiative)} hint={c.system === 'pf2e' ? 'Perception' : 'DEX mod'} />

        <HpCard c={c} update={update} />
      </div>

      {/* Abilities */}
      <section className="mb-6">
        <SectionTitle>Ability Scores</SectionTitle>
        <div className="grid grid-cols-3 gap-3 sm:grid-cols-6">
          {ABILITIES.map((a) => {
            const mod = sys.abilityModifier(c.abilities[a]);
            return (
              <div key={a} className="rounded-lg border border-line bg-panel p-3 text-center">
                <div className="text-xs font-semibold uppercase tracking-wide text-muted">{ABILITY_ABBR[a]}</div>
                <div className="my-1 font-display text-2xl font-bold text-accent">{formatModifier(mod)}</div>
                <NumberField
                  value={c.abilities[a]}
                  min={1}
                  max={30}
                  aria-label={`${ABILITY_ABBR[a]} score`}
                  onChange={(v) => update({ abilities: { ...c.abilities, [a]: v } })}
                />
              </div>
            );
          })}
        </div>
      </section>

      {/* Saves */}
      <section className="mb-6">
        <SectionTitle>Saving Throws</SectionTitle>
        <div className="grid gap-2 sm:grid-cols-2 lg:grid-cols-3">
          {c.system === 'pf2e'
            ? PF2E_SAVES.map((s) => (
                <RankRow
                  key={s.key}
                  label={s.label}
                  modifier={saves[s.ability]}
                  rank={(c.saveRanks[s.ability] as ProficiencyRank) ?? 'untrained'}
                  ranks={ranks}
                  onRank={(rank) => update({ saveRanks: { ...c.saveRanks, [s.ability]: rank } })}
                  system={c.system}
                />
              ))
            : ABILITIES.map((a) => (
                <RankRow
                  key={a}
                  label={`${ABILITY_ABBR[a]} save`}
                  modifier={saves[a]}
                  rank={(c.saveRanks[a] as ProficiencyRank) ?? 'untrained'}
                  ranks={ranks}
                  onRank={(rank) => update({ saveRanks: { ...c.saveRanks, [a]: rank } })}
                  system={c.system}
                />
              ))}
        </div>
      </section>

      {/* Skills */}
      <section className="mb-6">
        <SectionTitle>Skills</SectionTitle>
        <div className="grid gap-2 sm:grid-cols-2 lg:grid-cols-3">
          {skills.map((s) => (
            <RankRow
              key={s.key}
              label={`${s.label} (${ABILITY_ABBR[s.ability]})`}
              modifier={s.modifier}
              rank={(c.skillRanks[s.key] as ProficiencyRank) ?? 'untrained'}
              ranks={ranks}
              onRank={(rank) => update({ skillRanks: { ...c.skillRanks, [s.key]: rank } })}
              system={c.system}
            />
          ))}
        </div>
      </section>

      {/* Status & defenses (system-specific) */}
      <DefensesSection c={c} update={update} />

      {/* Attacks + passive perception */}
      <AttacksSection c={c} update={update} />

      {/* Spellcasting */}
      <SpellcastingSection c={c} update={update} />

      {/* Class resources + rest */}
      <ResourcesSection c={c} update={update} />

      {/* Inventory, currency, encumbrance */}
      <InventorySection c={c} update={update} />

      {/* Notes */}
      <section className="mb-6">
        <SectionTitle>Notes</SectionTitle>
        <textarea
          value={c.notes}
          onChange={(e) => update({ notes: e.target.value })}
          placeholder="Backstory, bonds, reminders…"
          className="min-h-32 w-full resize-y rounded-md border border-line bg-surface px-3 py-2 text-sm text-ink focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-accent/60"
        />
      </section>
    </Page>
  );
}

function HpCard({ c, update }: { c: Character; update: (p: Partial<Character>) => void }) {
  const [delta, setDelta] = useState(0);
  const apply = (mode: 'damage' | 'heal') => {
    if (!Number.isFinite(delta) || delta <= 0) return;
    if (mode === 'damage') {
      const absorbed = Math.min(c.hp.temp, delta);
      update({ hp: { ...c.hp, temp: c.hp.temp - absorbed, current: c.hp.current - (delta - absorbed) } });
    } else {
      update({ hp: { ...c.hp, current: Math.min(c.hp.max, c.hp.current + delta) } });
    }
    setDelta(0);
  };
  return (
    <div className="rounded-lg border border-line bg-panel p-4 text-center">
      <div className="text-xs font-semibold uppercase tracking-wide text-muted">Hit Points</div>
      <div className="my-1 font-display text-2xl font-bold text-ink">
        {c.hp.current}
        <span className="text-base text-muted"> / {c.hp.max}</span>
        {c.hp.temp > 0 && <span className="ml-1 text-base text-info">(+{c.hp.temp})</span>}
      </div>
      <div className="grid grid-cols-3 gap-1 text-[11px] text-muted">
        <label>Cur<NumberField value={c.hp.current} onChange={(current) => update({ hp: { ...c.hp, current } })} aria-label="Current HP" /></label>
        <label>Max<NumberField value={c.hp.max} min={0} onChange={(max) => update({ hp: { ...c.hp, max } })} aria-label="Max HP" /></label>
        <label>Temp<NumberField value={c.hp.temp} min={0} onChange={(temp) => update({ hp: { ...c.hp, temp } })} aria-label="Temp HP" /></label>
      </div>
      <div className="mt-2 flex items-center gap-1">
        <NumberField className="w-16" value={delta} min={0} onChange={setDelta} aria-label="HP change amount" />
        <Button size="sm" variant="danger" className="flex-1" onClick={() => apply('damage')}>
          Damage
        </Button>
        <Button size="sm" variant="secondary" className="flex-1" onClick={() => apply('heal')}>
          Heal
        </Button>
      </div>
    </div>
  );
}

function RankRow({
  label,
  modifier,
  rank,
  ranks,
  onRank,
  system,
}: {
  label: string;
  modifier: number;
  rank: ProficiencyRank;
  ranks: ProficiencyRank[];
  onRank: (r: ProficiencyRank) => void;
  system: SystemId;
}) {
  return (
    <div className="flex items-center gap-2 rounded-md border border-line bg-panel px-3 py-1.5">
      <button
        onClick={() => rollCheck(modifier, label, { system })}
        className="w-9 rounded font-display text-lg font-semibold text-accent hover:bg-accent/10"
        title={`Roll ${label}`}
      >
        {formatModifier(modifier)}
      </button>
      <span className="flex-1 truncate text-sm text-ink">{label}</span>
      <Select className="w-auto py-1 text-xs" value={rank} onChange={(e) => onRank(e.target.value as ProficiencyRank)}>
        {ranks.map((r) => (
          <option key={r} value={r}>
            {RANK_LABEL[r]}
          </option>
        ))}
      </Select>
    </div>
  );
}

function Labeled({ label, children }: { label: string; children: React.ReactNode }) {
  return (
    <label className="block">
      <span className="mb-1 block text-xs font-semibold uppercase tracking-wide text-muted">{label}</span>
      {children}
    </label>
  );
}

function StatCard({ label, value, hint, children }: { label: string; value: string | number; hint?: string; children?: React.ReactNode }) {
  return (
    <div className="rounded-lg border border-line bg-panel p-4 text-center">
      <div className="text-xs font-semibold uppercase tracking-wide text-muted">{label}</div>
      <div className="my-1 font-display text-3xl font-bold text-accent">{value}</div>
      {hint && <div className="text-xs text-muted">{hint}</div>}
      {children}
    </div>
  );
}

function SectionTitle({ children }: { children: React.ReactNode }) {
  return <h2 className="mb-2 font-display text-lg font-semibold text-ink">{children}</h2>;
}
