import { writable, get } from 'svelte/store'
import { streamChat, fetchSessions, fetchMessages, deleteSession as apiDeleteSession } from '$lib/api'
import type { ChatEvent, Session, Message } from '$lib/api'

export interface ChatMessage {
  id: string
  role: 'user' | 'assistant'
  text: string
  tools: ToolCallResult[]
}

export interface ToolCallResult {
  type: 'tool_use' | 'tool_result'
  name: string
  id?: string
  args?: any
  result?: any
  error?: string
}

function mid(): string {
  return crypto.randomUUID()
}

export const messages = writable<ChatMessage[]>([])
export const streaming = writable(false)
export const currentSession = writable<string | null>(null)
export const sessions = writable<Session[]>([])
export const sessionMessages = writable<Message[]>([])
export const error = writable<string | null>(null)

let activeController: AbortController | null = null

export async function loadSessions() {
  const list = await fetchSessions()
  sessions.set(list)
}

// mergeToolCalls collapses a persisted tool_calls array into one entry per
// call id. Nomos persists the tool_use and tool_result as two separate
// entries sharing the same id (matching the SSE event pair); Chat.svelte
// renders tools in a keyed {#each ... (tool.id)}, which throws on duplicate
// keys and silently aborts the whole message list. Live-streamed messages
// never hit this because sendMessage() merges tool_result into the existing
// tool_use entry in place rather than appending a second one.
function mergeToolCalls(raw: ToolCallResult[] | undefined): ToolCallResult[] {
  const byId = new Map<string, ToolCallResult>()
  for (const tc of raw ?? []) {
    const key = tc.id ?? crypto.randomUUID()
    const existing = byId.get(key)
    byId.set(key, existing ? { ...existing, ...tc, id: key } : { ...tc, id: key })
  }
  return Array.from(byId.values())
}

export async function loadSessionMessages(sessionId: string) {
  currentSession.set(sessionId)
  const msgs = await fetchMessages(sessionId)
  sessionMessages.set(msgs)
  const chatMsgs: ChatMessage[] = msgs.map((m) => ({
    id: m.id,
    role: m.role as 'user' | 'assistant',
    text: m.content?.text ?? (typeof m.content === 'string' ? m.content : ''),
    tools: mergeToolCalls(m.content?.tool_calls)
  }))
  messages.set(chatMsgs)
}

export function sendMessage(text: string) {
  error.set(null)
  streaming.set(true)

  const userMsg: ChatMessage = {
    id: mid(),
    role: 'user',
    text,
    tools: []
  }
  messages.update((ms) => [...ms, userMsg])

  const assistantMsg: ChatMessage = {
    id: mid(),
    role: 'assistant',
    text: '',
    tools: []
  }
  messages.update((ms) => [...ms, assistantMsg])

  let activeTools: Map<string, ToolCallResult> = new Map()

  activeController = streamChat(
    text,
    get(currentSession), // continue the active session so the agent keeps context
    (ev: ChatEvent) => {
      if (ev.type === 'session') {
        currentSession.set(ev.data)
      } else if (ev.type === 'tool_use') {
        const tr: ToolCallResult = {
          type: 'tool_use',
          name: ev.data.name,
          id: ev.data.id,
          args: ev.data.args
        }
        activeTools.set(ev.data.id, tr)
        messages.update((ms) => {
          const last = ms[ms.length - 1]
          if (last && last.role === 'assistant') {
            last.tools = [...last.tools, tr]
          }
          return [...ms]
        })
      } else if (ev.type === 'tool_result') {
        const existing = activeTools.get(ev.data.id)
        if (existing) {
          const updated: ToolCallResult = {
            ...existing,
            type: 'tool_result',
            result: ev.data.result,
            error: ev.data.error
          }
          activeTools.set(ev.data.id, updated)
          messages.update((ms) => {
            const last = ms[ms.length - 1]
            if (last && last.role === 'assistant') {
              last.tools = last.tools.map((t) =>
                t.id === ev.data.id ? updated : t
              )
            }
            return [...ms]
          })
        }
      } else if (ev.type === 'text_delta') {
        messages.update((ms) => {
          const last = ms[ms.length - 1]
          if (last && last.role === 'assistant') {
            last.text += ev.data
          }
          return [...ms]
        })
      } else if (ev.type === 'text') {
        // Final authoritative content for the turn; replaces accumulated deltas.
        messages.update((ms) => {
          const last = ms[ms.length - 1]
          if (last && last.role === 'assistant') {
            last.text = ev.data
          }
          return [...ms]
        })
      } else if (ev.type === 'done') {
        currentSession.set(ev.data?.session_id ?? ev.session_id)
      } else if (ev.type === 'error') {
        error.set(ev.data)
      }
    },
    (err: string) => {
      error.set(err)
    },
    () => {
      streaming.set(false)
      activeController = null
      loadSessions()
    }
  )
}

export function newChat() {
  cancelStream()
  currentSession.set(null)
  messages.set([])
  error.set(null)
}

export function cancelStream() {
  if (activeController) {
    activeController.abort()
    activeController = null
    streaming.set(false)
  }
}

export async function deleteSession(sessionId: string) {
  const ok = await apiDeleteSession(sessionId)
  if (!ok) return
  if (get(currentSession) === sessionId) {
    newChat()
  }
  loadSessions()
}