import { mkdir, writeFile } from 'fs/promises'
import { marked, type Tokens } from 'marked'
import { tmpdir } from 'os'
import { join } from 'path'
import React, { useRef } from 'react'
import type { CommandResultDisplay } from '../../commands.js'
import type { OptionWithDescription } from '../../components/CustomSelect/select.js'
import { Select } from '../../components/CustomSelect/select.js'
import { Byline, KeyboardShortcutHint, Pane } from '@anthropic/ink'
import { Box, setClipboard, Text, stringWidth, type KeyboardEvent } from '@anthropic/ink'
import { logEvent } from '../../services/analytics/index.js'
import type { LocalJSXCommandCall } from '../../types/command.js'
import type { AssistantMessage, Message } from '../../types/message.js'
import { getGlobalConfig, saveGlobalConfig } from '../../utils/config.js'
import { extractTextContent, stripPromptXMLTags } from '../../utils/messages.js'
import { countCharInString } from '../../utils/stringUtils.js'

const COPY_DIR = join(tmpdir(), 'claude')
const RESPONSE_FILENAME = 'response.md'
const MAX_LOOKBACK = 20

type CodeBlock = {
  code: string
  lang: string | undefined
}

function extractCodeBlocks(markdown: string): CodeBlock[] {
  const tokens = marked.lexer(stripPromptXMLTags(markdown))
  const blocks: CodeBlock[] = []
  for (const token of tokens) {
    if (token.type === 'code') {
      const codeToken = token as Tokens.Code
      blocks.push({ code: codeToken.text, lang: codeToken.lang })
    }
  }
  return blocks
}

/**
 * Walk messages newest-first, returning text from assistant messages that
 * actually said something (skips tool-use-only turns and API errors).
 * Index 0 = latest, 1 = second-to-latest, etc. Caps at MAX_LOOKBACK.
 */
export function collectRecentAssistantTexts(messages: Message[]): string[] {
  const texts: string[] = []
  for (
    let i = messages.length - 1;
    i >= 0 && texts.length < MAX_LOOKBACK;
    i--
  ) {
    const msg = messages[i]
    if (msg?.type !== 'assistant' || msg.isApiErrorMessage) continue
    const content = (msg as AssistantMessage).message.content
    if (!Array.isArray(content)) continue
    const text = extractTextContent(content, '\n\n')
    if (text) texts.push(text)
  }
  return texts
}

export function fileExtension(lang: string | undefined): string {
  if (lang) {
    // Sanitize to prevent path traversal (e.g. ```../../etc/passwd)
    // Language identifiers are alphanumeric: python, tsx, jsonc, etc.
    const sanitized = lang.replace(/[^a-zA-Z0-9]/g, '')
    if (sanitized && sanitized !== 'plaintext') {
      return `.${sanitized}`
    }
  }
  return '.txt'
}

async function writeToFile(text: string, filename: string): Promise<string> {
  const filePath = join(COPY_DIR, filename)
  await mkdir(COPY_DIR, { recursive: true })
  await writeFile(filePath, text, 'utf-8')
  return filePath
}

async function copyOrWriteToFile(
  text: string,
  filename: string,
): Promise<string> {
  const raw = await setClipboard(text)
  if (raw) process.stdout.write(raw)
  const lineCount = countCharInString(text, '\n') + 1
  const charCount = text.length
  // Also write to a temp file — clipboard paths are best-effort (OSC 52 needs
  // terminal support), so the file provides a reliable fallback.
  try {
    const filePath = await writeToFile(text, filename)
    return `Copied to clipboard (${charCount} characters, ${lineCount} lines)\nAlso written to ${filePath}`
  } catch {
    return `Copied to clipboard (${charCount} characters, ${lineCount} lines)`
  }
}

function truncateLine(text: string, maxLen: number): string {
  const firstLine = text.split('\n')[0] ?? ''
  if (stringWidth(firstLine) <= maxLen) {
    return firstLine
  }
  let result = ''
  let width = 0
  const targetWidth = maxLen - 1
  for (const char of firstLine) {
    const charWidth = stringWidth(char)
    if (width + charWidth > targetWidth) break
    result += char
    width += charWidth
  }
  return result + '\u2026'
}

type PickerProps = {
  fullText: string
  codeBlocks: CodeBlock[]
  messageAge: number
  onDone: (
    result?: string,
    options?: { display?: CommandResultDisplay },
  ) => void
}

type PickerSelection = number | 'full' | 'always'

function CopyPicker({
  fullText,
  codeBlocks,
  messageAge,
  onDone,
}: PickerProps): React.ReactNode {
  const focusedRef = useRef<PickerSelection>('full')

  const options: OptionWithDescription<PickerSelection>[] = [
    {
      label: 'Full response',
      value: 'full' as const,
      description: `${fullText.length} chars, ${countCharInString(fullText, '\n') + 1} lines`,
    },
    ...codeBlocks.map((block, index) => {
      const blockLines = countCharInString(block.code, '\n') + 1
      return {
        label: truncateLine(block.code, 60),
        value: index,
        description:
          [block.lang, blockLines > 1 ? `${blockLines} lines` : undefined]
            .filter(Boolean)
            .join(', ') || undefined,
      }
    }),
    {
      label: 'Always copy full response',
      value: 'always' as const,
      description: 'Skip this picker in the future (revert via /config)',
    },
  ]

  function getSelectionContent(selected: PickerSelection): {
    text: string
    filename: string
    blockIndex?: number
  } {
    if (selected === 'full' || selected === 'always') {
      return { text: fullText, filename: RESPONSE_FILENAME }
    }
    const block = codeBlocks[selected]!
    return {
      text: block.code,
      filename: `copy${fileExtension(block.lang)}`,
      blockIndex: selected,
    }
  }

  async function handleSelect(selected: PickerSelection): Promise<void> {
    const content = getSelectionContent(selected)
    if (selected === 'always') {
      if (!getGlobalConfig().copyFullResponse) {
        saveGlobalConfig(c => ({ ...c, copyFullResponse: true }))
      }
      logEvent('tengu_copy', {
        block_count: codeBlocks.length,
        always: true,
        message_age: messageAge,
      })
      const result = await copyOrWriteToFile(content.text, content.filename)
      onDone(
        `${result}\nPreference saved. Use /config to change copyFullResponse`,
      )
      return
    }
    logEvent('tengu_copy', {
      selected_block: content.blockIndex,
      block_count: codeBlocks.length,
      message_age: messageAge,
    })
    const result = await copyOrWriteToFile(content.text, content.filename)
    onDone(result)
  }

  async function handleWrite(selected: PickerSelection): Promise<void> {
    const content = getSelectionContent(selected)
    logEvent('tengu_copy', {
      selected_block: content.blockIndex,
      block_count: codeBlocks.length,
      message_age: messageAge,
      write_shortcut: true,
    })
    try {
      const filePath = await writeToFile(content.text, content.filename)
      onDone(`Written to ${filePath}`)
    } catch (e) {
      onDone(`Failed to write file: ${e instanceof Error ? e.message : e}`)
    }
  }

  function handleKeyDown(e: KeyboardEvent): void {
    if (e.key === 'w') {
      e.preventDefault()
      void handleWrite(focusedRef.current)
    }
  }

  return (
    <Pane>
      <Box
        flexDirection="column"
        gap={1}
        tabIndex={0}
        autoFocus
        onKeyDown={handleKeyDown}
      >
        <Text dimColor>Select content to copy:</Text>
        <Select<PickerSelection>
          options={options}
          hideIndexes={false}
          onFocus={value => {
            focusedRef.current = value
          }}
          onChange={selected => {
            void handleSelect(selected)
          }}
          onCancel={() => {
            onDone('Copy cancelled', { display: 'system' })
          }}
        />
        <Text dimColor>
          <Byline>
            <KeyboardShortcutHint shortcut="enter" action="copy" />
            <KeyboardShortcutHint shortcut="w" action="write to file" />
            <KeyboardShortcutHint shortcut="esc" action="cancel" />
          </Byline>
        </Text>
      </Box>
    </Pane>
  )
}

export const call: LocalJSXCommandCall = async (onDone, context, args) => {
  const texts = collectRecentAssistantTexts(context.messages)

  if (texts.length === 0) {
    onDone('No assistant message to copy')
    return null
  }

  // /copy N reaches back N-1 messages (1 = latest, 2 = second-to-latest, ...)
  let age = 0
  const arg = args?.trim()
  if (arg) {
    const n = Number(arg)
    if (!Number.isInteger(n) || n < 1) {
      onDone(`Usage: /copy [N] where N is 1 (latest), 2, 3, \u2026 Got: ${arg}`)
      return null
    }
    if (n > texts.length) {
      onDone(
        `Only ${texts.length} assistant ${texts.length === 1 ? 'message' : 'messages'} available to copy`,
      )
      return null
    }
    age = n - 1
  }

  const text = texts[age]!
  const codeBlocks = extractCodeBlocks(text)
  const config = getGlobalConfig()

  if (codeBlocks.length === 0 || config.copyFullResponse) {
    logEvent('tengu_copy', {
      always: config.copyFullResponse,
      block_count: codeBlocks.length,
      message_age: age,
    })
    const result = await copyOrWriteToFile(text, RESPONSE_FILENAME)
    onDone(result)
    return null
  }

  return (
    <CopyPicker
      fullText={text}
      codeBlocks={codeBlocks}
      messageAge={age}
      onDone={onDone}
    />
  )
}