'use client'

import { FormEvent, useMemo, useState } from 'react'
import { usePathname } from 'next/navigation'
import { getExplorerApiBase } from '@/services/api/blockscout'

interface AgentMessage {
  role: 'assistant' | 'user'
  content: string
}

const QUICK_PROMPTS = [
  'Explain this page',
  'Summarize the chain status',
  'Help me inspect a contract',
  'Find likely navigation issues',
] as const

export default function ExplorerAgentTool() {
  const pathname = usePathname() ?? '/'
  const [open, setOpen] = useState(false)
  const [input, setInput] = useState('')
  const [submitting, setSubmitting] = useState(false)
  const [messages, setMessages] = useState<AgentMessage[]>([
    {
      role: 'assistant',
      content:
        'DBIS Explorer AI Assist is ready. I can explain this page, summarize what you are looking at, and help investigate transactions, contracts, routes, and system surfaces.',
    },
  ])

  const pageContext = useMemo(
    () => ({
      path: pathname,
      view: 'explorer',
    }),
    [pathname],
  )

  const sendMessage = async (content: string) => {
    const trimmed = content.trim()
    if (!trimmed || submitting) return

    const nextMessages: AgentMessage[] = [...messages, { role: 'user', content: trimmed }]
    setMessages(nextMessages)
    setInput('')
    setSubmitting(true)

    try {
      const response = await fetch(`${getExplorerApiBase()}/api/v1/ai/chat`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({
          messages: nextMessages,
          pageContext,
        }),
      })

      const payload = await response.json().catch(() => null)
      if (!response.ok) {
        throw new Error(payload?.error?.message || `HTTP ${response.status}`)
      }

      const reply =
        payload?.message?.content ||
        payload?.reply ||
        'The agent did not return a readable reply.'

      setMessages((current) => [...current, { role: 'assistant', content: String(reply) }])
    } catch (error) {
      setMessages((current) => [
        ...current,
        {
          role: 'assistant',
          content:
            error instanceof Error
              ? `Agent tool is temporarily unavailable: ${error.message}`
              : 'Agent tool is temporarily unavailable.',
        },
      ])
    } finally {
      setSubmitting(false)
    }
  }

  const handleSubmit = async (event: FormEvent) => {
    event.preventDefault()
    await sendMessage(input)
  }

  return (
    <div className="fixed bottom-5 right-5 z-40 flex max-w-[calc(100vw-1.5rem)] flex-col items-end gap-3">
      {open ? (
        <section className="w-[min(24rem,calc(100vw-1.5rem))] overflow-hidden rounded-2xl border border-gray-200 bg-white shadow-2xl dark:border-gray-700 dark:bg-gray-900">
          <div className="flex items-start justify-between gap-3 border-b border-gray-200 px-4 py-3 dark:border-gray-700">
            <div>
              <h2 className="text-sm font-semibold text-gray-900 dark:text-white">DBIS Explorer AI Assist</h2>
              <p className="mt-1 text-xs text-gray-500 dark:text-gray-400">
                Page-aware guidance for the explorer. Helpful, read-only, and designed for quick investigation.
              </p>
            </div>
            <button
              type="button"
              onClick={() => setOpen(false)}
              className="rounded-lg px-2 py-1 text-xs font-medium text-gray-500 hover:bg-gray-100 hover:text-gray-800 dark:text-gray-400 dark:hover:bg-gray-800 dark:hover:text-gray-200"
            >
              Close
            </button>
          </div>
          <div className="flex flex-wrap gap-2 border-b border-gray-200 px-4 py-3 dark:border-gray-700">
            {QUICK_PROMPTS.map((prompt) => (
              <button
                key={prompt}
                type="button"
                onClick={() => void sendMessage(prompt)}
                className="rounded-full border border-primary-200 bg-primary-50 px-3 py-1 text-xs font-medium text-primary-700 hover:bg-primary-100 dark:border-primary-500/30 dark:bg-primary-500/10 dark:text-primary-300 dark:hover:bg-primary-500/20"
              >
                {prompt}
              </button>
            ))}
          </div>
          <div className="max-h-[22rem] space-y-3 overflow-y-auto px-4 py-3">
            {messages.map((message, index) => (
              <div
                key={`${message.role}-${index}`}
                className={`rounded-2xl px-3 py-2 text-sm ${
                  message.role === 'assistant'
                    ? 'bg-gray-100 text-gray-800 dark:bg-gray-800 dark:text-gray-100'
                    : 'ml-6 bg-primary-600 text-white'
                }`}
              >
                {message.content}
              </div>
            ))}
          </div>
          <form onSubmit={handleSubmit} className="border-t border-gray-200 px-4 py-3 dark:border-gray-700">
            <label className="block">
              <span className="sr-only">Ask the explorer agent</span>
              <textarea
                value={input}
                onChange={(event) => setInput(event.target.value)}
                rows={3}
                placeholder="Ask about this page, a transaction, a token, or an access-control flow."
                className="w-full rounded-xl border border-gray-300 px-3 py-2 text-sm focus:border-primary-500 focus:outline-none focus:ring-2 focus:ring-primary-200 dark:border-gray-700 dark:bg-gray-950 dark:text-white"
              />
            </label>
            <div className="mt-3 flex items-center justify-between gap-3">
              <p className="text-xs text-gray-500 dark:text-gray-400">Current view: {pathname}</p>
              <button
                type="submit"
                disabled={submitting || !input.trim()}
                className="rounded-xl bg-primary-600 px-4 py-2 text-sm font-semibold text-white transition hover:bg-primary-700 disabled:cursor-not-allowed disabled:opacity-60"
              >
                {submitting ? 'Thinking…' : 'Send'}
              </button>
            </div>
          </form>
        </section>
      ) : null}

      <button
        type="button"
        onClick={() => setOpen((value) => !value)}
        className="inline-flex items-center gap-2 rounded-full bg-primary-600 p-3 text-sm font-semibold text-white shadow-lg transition hover:bg-primary-700 lg:px-4 lg:py-3"
        aria-expanded={open}
        aria-label="Open DBIS Explorer AI Assist"
      >
        <span className="inline-flex h-7 w-7 items-center justify-center rounded-full bg-white/15">
          <svg className="h-4 w-4" viewBox="0 0 24 24" fill="none" stroke="currentColor" aria-hidden>
            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M8 10h.01M12 10h.01M16 10h.01M9 16H5a2 2 0 01-2-2V6a2 2 0 012-2h14a2 2 0 012 2v8a2 2 0 01-2 2h-4l-4 4v-4Z" />
          </svg>
        </span>
        <span className="hidden lg:inline">AI Assist</span>
      </button>
    </div>
  )
}