import { formatFrontmatter } from "../utils/frontmatter"
import type { ClaudeAgent, ClaudeCommand, ClaudeMcpServer, ClaudePlugin } from "../types/claude"
import type {
  PiBundle,
  PiGeneratedSkill,
  PiMcporterConfig,
  PiMcporterServer,
} from "../types/pi"
import type { ClaudeToOpenCodeOptions } from "./claude-to-opencode"
import { PI_COMPAT_EXTENSION_SOURCE } from "../templates/pi/compat-extension"

export type ClaudeToPiOptions = ClaudeToOpenCodeOptions

const PI_DESCRIPTION_MAX_LENGTH = 1024

export function convertClaudeToPi(
  plugin: ClaudePlugin,
  _options: ClaudeToPiOptions,
): PiBundle {
  const promptNames = new Set<string>()
  const usedSkillNames = new Set<string>(plugin.skills.map((skill) => normalizeName(skill.name)))

  const prompts = plugin.commands
    .filter((command) => !command.disableModelInvocation)
    .map((command) => convertPrompt(command, promptNames))

  const generatedSkills = plugin.agents.map((agent) => convertAgent(agent, usedSkillNames))

  const extensions = [
    {
      name: "compound-engineering-compat.ts",
      content: PI_COMPAT_EXTENSION_SOURCE,
    },
  ]

  return {
    prompts,
    skillDirs: plugin.skills.map((skill) => ({
      name: skill.name,
      sourceDir: skill.sourceDir,
    })),
    generatedSkills,
    extensions,
    mcporterConfig: plugin.mcpServers ? convertMcpToMcporter(plugin.mcpServers) : undefined,
  }
}

function convertPrompt(command: ClaudeCommand, usedNames: Set<string>) {
  const name = uniqueName(normalizeName(command.name), usedNames)
  const frontmatter: Record<string, unknown> = {
    description: command.description,
    "argument-hint": command.argumentHint,
  }

  let body = transformContentForPi(command.body)
  body = appendCompatibilityNoteIfNeeded(body)

  return {
    name,
    content: formatFrontmatter(frontmatter, body.trim()),
  }
}

function convertAgent(agent: ClaudeAgent, usedNames: Set<string>): PiGeneratedSkill {
  const name = uniqueName(normalizeName(agent.name), usedNames)
  const description = sanitizeDescription(
    agent.description ?? `Converted from Claude agent ${agent.name}`,
  )

  const frontmatter: Record<string, unknown> = {
    name,
    description,
  }

  const sections: string[] = []
  if (agent.capabilities && agent.capabilities.length > 0) {
    sections.push(`## Capabilities\n${agent.capabilities.map((capability) => `- ${capability}`).join("\n")}`)
  }

  const body = [
    ...sections,
    agent.body.trim().length > 0
      ? agent.body.trim()
      : `Instructions converted from the ${agent.name} agent.`,
  ].join("\n\n")

  return {
    name,
    content: formatFrontmatter(frontmatter, body),
  }
}

function transformContentForPi(body: string): string {
  let result = body

  // Task repo-research-analyst(feature_description)
  // -> Run subagent with agent="repo-research-analyst" and task="feature_description"
  const taskPattern = /^(\s*-?\s*)Task\s+([a-z][a-z0-9-]*)\(([^)]+)\)/gm
  result = result.replace(taskPattern, (_match, prefix: string, agentName: string, args: string) => {
    const skillName = normalizeName(agentName)
    const trimmedArgs = args.trim().replace(/\s+/g, " ")
    return `${prefix}Run subagent with agent=\"${skillName}\" and task=\"${trimmedArgs}\".`
  })

  // Claude-specific tool references
  result = result.replace(/\bAskUserQuestion\b/g, "ask_user_question")
  result = result.replace(/\bTodoWrite\b/g, "file-based todos (todos/ + /skill:file-todos)")
  result = result.replace(/\bTodoRead\b/g, "file-based todos (todos/ + /skill:file-todos)")

  // /command-name or /workflows:command-name -> /workflows-command-name
  const slashCommandPattern = /(?<![:\w])\/([a-z][a-z0-9_:-]*?)(?=[\s,."')\]}`]|$)/gi
  result = result.replace(slashCommandPattern, (match, commandName: string) => {
    if (commandName.includes("/")) return match
    if (["dev", "tmp", "etc", "usr", "var", "bin", "home"].includes(commandName)) {
      return match
    }

    if (commandName.startsWith("skill:")) {
      const skillName = commandName.slice("skill:".length)
      return `/skill:${normalizeName(skillName)}`
    }

    const withoutPrefix = commandName.startsWith("prompts:")
      ? commandName.slice("prompts:".length)
      : commandName

    return `/${normalizeName(withoutPrefix)}`
  })

  return result
}

function appendCompatibilityNoteIfNeeded(body: string): string {
  if (!/\bmcp\b/i.test(body)) return body

  const note = [
    "",
    "## Pi + MCPorter note",
    "For MCP access in Pi, use MCPorter via the generated tools:",
    "- `mcporter_list` to inspect available MCP tools",
    "- `mcporter_call` to invoke a tool",
    "",
  ].join("\n")

  return body + note
}

function convertMcpToMcporter(servers: Record<string, ClaudeMcpServer>): PiMcporterConfig {
  const mcpServers: Record<string, PiMcporterServer> = {}

  for (const [name, server] of Object.entries(servers)) {
    if (server.command) {
      mcpServers[name] = {
        command: server.command,
        args: server.args,
        env: server.env,
        headers: server.headers,
      }
      continue
    }

    if (server.url) {
      mcpServers[name] = {
        baseUrl: server.url,
        headers: server.headers,
      }
    }
  }

  return { mcpServers }
}

function normalizeName(value: string): string {
  const trimmed = value.trim()
  if (!trimmed) return "item"
  const normalized = trimmed
    .toLowerCase()
    .replace(/[\\/]+/g, "-")
    .replace(/[:\s]+/g, "-")
    .replace(/[^a-z0-9_-]+/g, "-")
    .replace(/-+/g, "-")
    .replace(/^-+|-+$/g, "")
  return normalized || "item"
}

function sanitizeDescription(value: string, maxLength = PI_DESCRIPTION_MAX_LENGTH): string {
  const normalized = value.replace(/\s+/g, " ").trim()
  if (normalized.length <= maxLength) return normalized
  const ellipsis = "..."
  return normalized.slice(0, Math.max(0, maxLength - ellipsis.length)).trimEnd() + ellipsis
}

function uniqueName(base: string, used: Set<string>): string {
  if (!used.has(base)) {
    used.add(base)
    return base
  }
  let index = 2
  while (used.has(`${base}-${index}`)) {
    index += 1
  }
  const name = `${base}-${index}`
  used.add(name)
  return name
}