import { useCallback, useEffect, useState } from 'react'
import { MapEditor } from './MapView.jsx'

const J = { 'Content-Type': 'application/json' }
const errText = async (r, fallback) => {
  if (r.status === 413) return 'The file is too big for the web server (nginx client_max_body_size). Use a smaller image or ask the server admin to raise the limit.'
  return (await r.json().catch(() => ({}))).detail || fallback
}

// Big images are scaled down and re-encoded in the browser first (the server does it again anyway), so they fit through proxies with small upload limits.
async function shrink(f) {
  if (f.size < 900_000) return f
  try {
    const bmp = await createImageBitmap(f)
    const k = Math.min(1, 4096 / Math.max(bmp.width, bmp.height))
    const c = document.createElement('canvas')
    c.width = Math.max(1, Math.round(bmp.width * k)); c.height = Math.max(1, Math.round(bmp.height * k))
    c.getContext('2d').drawImage(bmp, 0, 0, c.width, c.height)
    const blob = await new Promise((res) => c.toBlob(res, 'image/webp', 0.9))
    return blob && blob.size < f.size ? blob : f
  } catch { return f }
}

function SharePanel({ m, reload }) {
  const [name, setName] = useState('')
  const [err, setErr] = useState('')
  const add = async (e) => {
    e.preventDefault()
    setErr('')
    const r = await fetch(`/api/maps/${m.id}/shares`, { method: 'POST', headers: J, body: JSON.stringify({ username: name }) })
    if (!r.ok) return setErr(await errText(r, 'Could not share.'))
    setName(''); reload()
  }
  const remove = async (u) => { await fetch(`/api/maps/${m.id}/shares/${encodeURIComponent(u)}`, { method: 'DELETE' }).catch(() => {}); reload() }
  return (
    <div className="sharepanel">
      <div className="small muted">Shared with</div>
      <div className="chips">
        {m.shared_with.length === 0 && <span className="small muted">Nobody yet.</span>}
        {m.shared_with.map((u) => <span key={u} className="chip">{u} <button className="ghost" aria-label={`Stop sharing with ${u}`} onClick={() => remove(u)}>×</button></span>)}
      </div>
      <form className="row" onSubmit={add}>
        <input value={name} onChange={(e) => setName(e.target.value)} placeholder="Username" aria-label="Username to share with" />
        <button type="submit" disabled={!name.trim()}>Share</button>
      </form>
      {err && <p className="warn small">{err}</p>}
    </div>
  )
}

// All maps of the user (prepare, share, copy) plus the maps other users shared with them
export default function Maps() {
  const [list, setList] = useState(null)
  const [editing, setEditing] = useState(null)
  const [open, setOpen] = useState(null)
  const [err, setErr] = useState('')
  const [busy, setBusy] = useState(false)
  const load = useCallback(() => fetch('/api/maps').then((r) => (r.ok ? r.json() : [])).then(setList).catch(() => setList([])), [])
  useEffect(() => { load() }, [load, editing])
  const upload = async (e) => {
    const f = e.target.files?.[0]
    e.target.value = ''
    if (!f) return
    setErr(''); setBusy(true)
    const body = await shrink(f)
    const r = await fetch(`/api/maps?name=${encodeURIComponent(f.name.replace(/\.[^.]+$/, ''))}`, { method: 'POST', headers: { 'Content-Type': body.type || 'application/octet-stream' }, body }).catch(() => null)
    setBusy(false)
    if (!r || !r.ok) return setErr(r ? await errText(r, 'Upload failed') : 'Upload failed')
    load()
  }
  const copy = async (m) => {
    const r = await fetch(`/api/maps/${m.id}/copy`, { method: 'POST' })
    if (!r.ok) return setErr(await errText(r, 'Could not copy'))
    load()
  }
  const del = async (m) => {
    if (!window.confirm(`Delete the map "${m.name}"? Lobbies that show it get an empty table, shared users lose it.`)) return
    await fetch(`/api/maps/${m.id}`, { method: 'DELETE' }); load()
  }
  const mine = (list || []).filter((m) => m.mine), shared = (list || []).filter((m) => !m.mine)
  const card = (m) => (
    <li key={m.id} className="mapcard card">
      <img src={`/api/maps/${m.id}/thumb`} alt="" loading="lazy" />
      <div className="mapcardbody">
        <strong>{m.name}</strong>
        <span className="small muted">{m.w}×{m.h} · {m.tokens} token{m.tokens === 1 ? '' : 's'} · {m.walls} wall{m.walls === 1 ? '' : 's'}{!m.mine && ` · from ${m.author}`}{m.mine && m.shared_with.length > 0 && ` · shared with ${m.shared_with.join(', ')}`}</span>
        <span className="row">
          {m.mine && <button className="on" onClick={() => setEditing(m.id)}>Edit</button>}
          {m.mine && <button className="ghost" onClick={() => setOpen(open === m.id ? null : m.id)}>Share</button>}
          <button className="ghost" onClick={() => copy(m)} title="Make your own editable copy">{m.mine ? 'Duplicate' : 'Copy to my maps'}</button>
          {m.mine && <button className="ghost danger" onClick={() => del(m)}>Delete</button>}
        </span>
        {open === m.id && m.mine && <SharePanel m={m} reload={load} />}
      </div>
    </li>
  )
  return (
    <section className="page">
      <h1>Maps</h1>
      <p className="muted">Prepare maps with grid, enemies, NPCs, walls and doors. The DM puts one on the table from a lobby (<em>Lobby actions</em>). Shared maps can be used on your table or copied, but not changed.</p>
      <label className="uploadbtn">{busy ? 'Uploading …' : '+ Upload map (PNG, JPEG, WebP, up to 12 MB)'}<input type="file" accept="image/png,image/jpeg,image/webp" onChange={upload} disabled={busy} hidden /></label>
      {err && <p className="warn">{err}</p>}
      {list === null && <p className="muted">Loading …</p>}
      {list && !mine.length && <p className="muted">You have no maps yet.</p>}
      <ul className="mapcards">{mine.map(card)}</ul>
      {shared.length > 0 && <><h2>Shared with me</h2><ul className="mapcards">{shared.map(card)}</ul></>}
      {editing && <MapEditor id={editing} onClose={() => setEditing(null)} />}
    </section>
  )
}