import Anthropic from '@anthropic-ai/sdk'
import type { AIPayload, Attachment } from '../renderer/types/editor'
import type { DraftDocument } from './fileSystem'

let _client: Anthropic | null = null

function getClient(): Anthropic {
  if (!_client) {
    const apiKey = process.env.ANTHROPIC_API_KEY
if (!apiKey || apiKey === 'your-api-key-here') {
      throw new Error(
        'ANTHROPIC_API_KEY is not set. Add it to app/.env.local'
      )
    }
    _client = new Anthropic({ apiKey })
  }
  return _client
}

const MAX_MANUSCRIPT_CHARS = 560_000 // ~140k tokens at 4 chars/token

function buildStoryBibleBlock(content: string): string {
  return [
    '=== STORY BIBLE ===',
    "The following is the author's curated reference document. Treat it as authoritative ground truth for characters, world, timeline, and consistency rules.",
    '',
    content,
    '=== END STORY BIBLE ==='
  ].join('\n')
}

function buildManuscriptBlock(allDocs: DraftDocument[], currentPath: string): string {
  const total = allDocs.length
  const totalChars = allDocs.reduce((s, d) => s + d.content.length, 0)
  let docs = allDocs
  let truncatedCount = 0

  if (totalChars > MAX_MANUSCRIPT_CHARS) {
    const currentIdx = allDocs.findIndex(d => d.path === currentPath)
    const pivot = currentIdx !== -1 ? currentIdx : 0
    const priority: number[] = [pivot]
    let lo = pivot - 1
    let hi = pivot + 1
    while (lo >= 0 || hi < allDocs.length) {
      if (hi < allDocs.length) priority.push(hi++)
      if (lo >= 0) priority.push(lo--)
    }
    let budget = MAX_MANUSCRIPT_CHARS
    const included = new Set<number>()
    for (const idx of priority) {
      if (budget <= 0) break
      if (budget - allDocs[idx].content.length >= 0) {
        budget -= allDocs[idx].content.length
        included.add(idx)
      }
    }
    truncatedCount = allDocs.length - included.size
    docs = allDocs.filter((_, i) => included.has(i))
  }

  const lines: string[] = [
    '=== MANUSCRIPT: Full Story Context ===',
    `The following ${docs.length} chapter(s) contain the novel in narrative order.`,
    'Use them for cross-chapter analysis: consistency, character arcs, narrative structure.',
    ''
  ]
  for (let i = 0; i < docs.length; i++) {
    lines.push(`--- [${i + 1}/${total}] ${docs[i].relativePath} ---`)
    lines.push(docs[i].content)
    lines.push('')
  }
  if (truncatedCount > 0) {
    lines.push(`[Note: ${truncatedCount} chapter(s) omitted to fit context. Chapters closest to the current chapter were prioritised.]`)
  }
  lines.push('=== END MANUSCRIPT ===')
  return lines.join('\n')
}

function buildSystemPrompt(payload: AIPayload, allDocs?: DraftDocument[], storyBibleContent?: string): string {
  const chapterName =
    payload.documentPath.split('/').pop()?.replace(/\.md$/, '') ?? 'Unknown chapter'

  const storyBibleSection = storyBibleContent
    ? buildStoryBibleBlock(storyBibleContent) + '\n\n'
    : ''

  const manuscriptSection = allDocs
    ? buildManuscriptBlock(allDocs, payload.documentPath) + '\n\n'
    : ''

  const chapterContext = `${storyBibleSection}${manuscriptSection}You are a literary editor assistant helping with a gothic/historical fiction novel set in the Basque Country. The current chapter is: "${chapterName}".

Key characters: Esti, Marko, Garbi, Irati, Cardinal Nikolai, Amaya, Izotz, Sua, Señor Jiménez, the Genboa family.

The chapter text is provided below. When identifying specific passages, quote the EXACT text from the document so it can be located and highlighted in the editor.

--- CHAPTER ---
${payload.documentContent}
--- END CHAPTER ---`

  const modeInstructions: Record<AIPayload['mode'], string> = {
    chat: 'Answer questions about the chapter, characters, plot, or craft. Be specific and cite passages where relevant.',

    passive_voice: `Identify ALL instances of passive voice in this chapter.

For each instance, respond in this exact format:
PASSIVE: "[exact quoted sentence]"
WHY: [brief explanation]
SUGGESTION: "[rewritten in active voice]"

List every instance you find, then give a brief overall summary.`,

    consistency: `Check this chapter carefully for consistency issues:
- Character names spelled or used inconsistently
- Timeline contradictions or impossibilities
- Repeated words or phrases appearing too close together (within a page)
- Setting details that seem contradictory
- Character behaviour inconsistent with their established personality

For each issue found:
ISSUE: [type of issue]
PASSAGE: "[exact quoted text]"
PROBLEM: [explanation]
SUGGESTION: [how to fix it]`,

    style: `Analyze the writing style and provide specific improvement suggestions:
- Pacing: identify slow passages or rushed moments
- Sentence variety: flag runs of similar length or structure
- Gothic atmosphere: passages where the atmospheric tone is inconsistent
- Dialogue: any dialogue that feels stilted or unnatural

For each suggestion:
ISSUE: [type: Pacing / Sentence Variety / Atmosphere / Dialogue]
PASSAGE: "[exact quoted text]"
PROBLEM: [specific explanation]
SUGGESTION: [concrete rewrite or approach]`,

    show_tell: `Identify every passage in this chapter where the author tells the reader something that should instead be shown through action, dialogue, sensation, or concrete detail.

Focus on:
- Emotions or inner states stated directly ("she felt afraid", "he was relieved") instead of expressed through physical reaction or behaviour
- Character motivations or intentions explained by the narrator rather than revealed through what characters do or say
- Abstract or evaluative description ("the room was oppressive", "it was a beautiful day") instead of specific sensory detail that lets the reader feel it
- Dialogue tags or beats that tell the reader how something was said rather than letting word choice and action carry it

For each instance:
ISSUE: Show Don't Tell
PASSAGE: "[exact quoted text from the chapter]"
PROBLEM: [one sentence explaining what is being told that should be shown]
SUGGESTION: "[a concrete rewrite that shows the same moment through action, sensation, or dialogue]"`,

    critique: `Give an honest, detailed critique of this chapter as a whole. Structure your response as follows:

**Overall impression** (2–3 sentences on what the chapter achieves and its most significant weakness)

**What works well**
Identify 2–4 specific strengths — scenes, lines, or moments that land effectively. Quote the passage and explain why it works.

STRENGTH: "[exact quoted passage]"
WHY: [explanation]

**What needs work**
Identify 2–4 areas where the chapter falls short. Be direct. Quote the passage and give a concrete direction for improvement.

ISSUE: "[exact quoted passage]"
PROBLEM: [explanation]
SUGGESTION: [concrete direction]

**One priority**
Name the single most important thing to fix in a revision of this chapter.`
  }

  let prompt = `${chapterContext}\n\n${modeInstructions[payload.mode]}`

  if (payload.attachments && payload.attachments.length > 0) {
    const names = payload.attachments.map((a) => a.name).join(', ')
    prompt += `\n\n---
ATTACHED REFERENCE MATERIAL: ${names}

The user has provided reference file(s) above. Based on these references and the user's instruction, identify specific passages in the chapter that should be changed.

You MUST output every suggested edit in this exact structured format — no other format will create highlights in the editor:

ISSUE: [short category label, e.g. "Tone", "Vocabulary", "Style Match", "Pacing"]
PASSAGE: "[copy the exact verbatim text from the chapter — at least 10 characters, unique enough to be found]"
PROBLEM: [one sentence explaining why this passage needs changing in light of the reference material]
SUGGESTION: "[the revised replacement text]"

Rules:
- PASSAGE must be a verbatim copy of text that exists in the chapter above. Do not paraphrase.
- Include as many ISSUE/PASSAGE/PROBLEM/SUGGESTION blocks as are genuinely warranted.
- After all structured blocks, you may add a brief overall summary.
---`
  }

  return prompt
}

type UserContentBlock = Anthropic.ImageBlockParam | Anthropic.TextBlockParam

function buildUserContent(
  userMessage: string,
  attachments: Attachment[] | undefined
): string | UserContentBlock[] {
  if (!attachments || attachments.length === 0) {
    return userMessage
  }

  const content: UserContentBlock[] = []

  for (const att of attachments) {
    if (att.mimeType.startsWith('image/')) {
      content.push({
        type: 'image',
        source: {
          type: 'base64',
          media_type: att.mimeType as 'image/jpeg' | 'image/png' | 'image/gif' | 'image/webp',
          data: att.data
        }
      })
    } else {
      // Text or PDF — include as a fenced text block
      content.push({
        type: 'text',
        text: `--- Attached: ${att.name} ---\n${att.data}\n--- End of ${att.name} ---`
      })
    }
  }

  content.push({ type: 'text', text: userMessage })
  return content
}

export async function streamMessage(
  payload: AIPayload,
  allDocs: DraftDocument[] | undefined,
  storyBibleContent: string | undefined,
  onChunk: (chunk: string) => void
): Promise<void> {
  const client = getClient()

  const messages: Anthropic.MessageParam[] = [
    ...payload.conversationHistory.slice(-10),
    {
      role: 'user' as const,
      content: buildUserContent(payload.userMessage, payload.attachments)
    }
  ]

  const stream = client.messages.stream({
    model: 'claude-sonnet-4-5',
    max_tokens: 4096,
    system: buildSystemPrompt(payload, allDocs, storyBibleContent),
    messages
  })

  for await (const chunk of stream) {
    if (
      chunk.type === 'content_block_delta' &&
      chunk.delta.type === 'text_delta'
    ) {
      onChunk(chunk.delta.text)
    }
  }
}