'use client'

import { useEffect, useMemo, useState } from 'react'
import { useRouter } from 'next/navigation'
import { authFetch, clearToken, getApiBase, getToken } from '../lib/auth'

type SiteInfo = {
  changelog?: string
}

type ChangelogGroup = {
  date: string
  entries: string[]
}

const DATE_PATTERN = /^\d{4}-\d{2}-\d{2}$/

const parseChangelog = (raw: string): ChangelogGroup[] => {
  const groups: ChangelogGroup[] = []
  for (const rawLine of raw.split('\n')) {
    const line = rawLine.trim()
    if (!line) continue
    const [candidateDate, ...messageParts] = line.split('|')
    if (DATE_PATTERN.test(candidateDate) && messageParts.length > 0) {
      const message = messageParts.join('|').trim()
      if (!message) continue
      const currentGroup = groups[groups.length - 1]
      if (currentGroup?.date === candidateDate) {
        currentGroup.entries.push(message)
      } else {
        groups.push({ date: candidateDate, entries: [message] })
      }
      continue
    }
    if (groups.length === 0) {
      groups.push({ date: 'Updates', entries: [line] })
    } else {
      groups[groups.length - 1].entries.push(line)
    }
  }
  return groups
}

export default function ChangelogPage() {
  const router = useRouter()
  const [groups, setGroups] = useState<ChangelogGroup[]>([])
  const [loading, setLoading] = useState(true)

  useEffect(() => {
    const token = getToken()
    if (!token) {
      router.push('/login')
      return
    }
    let active = true
    const load = async () => {
      try {
        const baseUrl = getApiBase()
        const response = await authFetch(`${baseUrl}/site/info`)
        if (!response.ok) {
          if (response.status === 401) {
            clearToken()
            router.push('/login')
            return
          }
          throw new Error('Failed to load changelog')
        }
        const data: SiteInfo = await response.json()
        if (!active) return
        setGroups(parseChangelog(data?.changelog ?? ''))
      } catch (err) {
        console.error(err)
        if (!active) return
        setGroups([])
      } finally {
        if (active) setLoading(false)
      }
    }
    void load()
    return () => {
      active = false
    }
  }, [router])

  const content = useMemo(() => {
    if (loading) {
      return <div className="loading-text">Loading changelog...</div>
    }
    if (groups.length === 0) {
      return <div className="meta">No updates posted yet.</div>
    }
    return (
      <div className="changelog-groups">
        {groups.map((group) => (
          <section key={group.date} className="changelog-group">
            <h2>{group.date}</h2>
            <ul className="changelog-list">
              {group.entries.map((entry, index) => (
                <li key={`${group.date}-${entry}-${index}`}>{entry}</li>
              ))}
            </ul>
          </section>
        ))}
      </div>
    )
  }, [groups, loading])

  return (
    <div className="page">
      <section className="card changelog-card">
        <div className="changelog-header">
          <h1>Changelog</h1>
          <p className="lede">Latest updates and release notes.</p>
        </div>
        {content}
      </section>
    </div>
  )
}