// Debug session manager: adapter catalog, launch/attach, stop tracking, child sessions.
import fs from 'node:fs'
import net from 'node:net'
import os from 'node:os'
import path from 'node:path'
import { execFileSync } from 'node:child_process'
import { DapClient } from './dap.js'

const HOME = os.homedir()

function which(cmd) {
  if (path.isAbsolute(cmd)) return fs.existsSync(cmd) ? cmd : null
  for (const d of [...(process.env.PATH || '').split(path.delimiter), path.join(HOME, '.local/bin'), '/usr/local/bin']) {
    if (!d) continue
    const p = path.join(d, cmd)
    try { fs.accessSync(p, fs.constants.X_OK); return p } catch {}
  }
  return null
}

function pythonWithDebugpy() {
  for (const py of ['python3', 'python']) {
    const p = which(py)
    if (!p) continue
    try { execFileSync(p, ['-c', 'import debugpy'], { stdio: 'ignore', timeout: 10000 }); return p } catch {}
  }
  return null
}

function jsDebugServer() {
  const cands = [process.env.JS_DEBUG_DAP, path.join(HOME, '.local/share/js-debug/js-debug/src/dapDebugServer.js')].filter(Boolean)
  return cands.find((c) => fs.existsSync(c)) ?? null
}

const freePort = () => new Promise((resolve, reject) => {
  const s = net.createServer()
  s.listen(0, '127.0.0.1', () => { const { port } = s.address(); s.close(() => resolve(port)) })
  s.on('error', reject)
})

/**
 * Adapter catalog. `detect()` returns spawn info or null; `launchArgs`/`attachArgs` build the
 * DAP request arguments.
 */
export const ADAPTERS = {
  debugpy: {
    languages: ['python'], extensions: ['.py'],
    detect: () => { const py = pythonWithDebugpy(); return py ? { kind: 'stdio', command: py, args: ['-m', 'debugpy.adapter'] } : null },
    install: 'pip install --user debugpy',
    launchArgs: ({ program, args, cwd, env, stopOnEntry }) => ({ type: 'python', request: 'launch', program, args, cwd, env, stopOnEntry: !!stopOnEntry, console: 'internalConsole', justMyCode: false, redirectOutput: true }),
    attachArgs: ({ host, port, pid }) => (pid ? { type: 'python', request: 'attach', processId: pid, justMyCode: false } : { type: 'python', request: 'attach', connect: { host: host ?? '127.0.0.1', port }, justMyCode: false }),
  },
  node: {
    languages: ['javascript', 'typescript'], extensions: ['.js', '.mjs', '.cjs', '.ts', '.mts'],
    detect: () => { const s = jsDebugServer(); return s ? { kind: 'tcp-server', command: process.execPath, scriptArgs: (port) => [s, String(port), '127.0.0.1'] } : null },
    install: 'download js-debug-dap from github.com/microsoft/vscode-js-debug/releases into ~/.local/share/js-debug',
    launchArgs: ({ program, args, cwd, env, stopOnEntry }) => ({ type: 'pwa-node', request: 'launch', program, args, cwd, env, stopOnEntry: !!stopOnEntry, console: 'internalConsole', outputCapture: 'std', runtimeExecutable: which('node') ?? process.execPath, skipFiles: ['<node_internals>/**'] }),
    attachArgs: ({ host, port, pid }) => (pid ? { type: 'pwa-node', request: 'attach', processId: String(pid) } : { type: 'pwa-node', request: 'attach', address: host ?? '127.0.0.1', port }),
  },
  'lldb-dap': {
    languages: ['c', 'cpp', 'rust', 'swift'], extensions: ['', '.out', '.bin'],
    detect: () => { const b = which('lldb-dap') ?? which('lldb-vscode'); return b ? { kind: 'stdio', command: b, args: [] } : null },
    install: 'apt install lldb (provides lldb-dap)',
    launchArgs: ({ program, args, cwd, env, stopOnEntry }) => ({ type: 'lldb-dap', request: 'launch', program, args, cwd, env: Object.entries(env ?? {}).map(([k, v]) => `${k}=${v}`), stopOnEntry: !!stopOnEntry }),
    attachArgs: ({ pid }) => ({ type: 'lldb-dap', request: 'attach', pid }),
  },
  gdb: {
    languages: ['c', 'cpp', 'rust', 'go', 'fortran'], extensions: ['', '.out', '.bin'],
    detect: () => {
      const b = which('gdb')
      if (!b) return null
      try { const v = execFileSync(b, ['--version'], { encoding: 'utf8' }); const m = /(\d+)\.\d+/.exec(v); if (!m || Number(m[1]) < 14) return null } catch { return null }
      return { kind: 'stdio', command: b, args: ['--interpreter=dap'] }
    },
    install: 'apt install gdb (>= 14 has --interpreter=dap)',
    launchArgs: ({ program, args, cwd, stopOnEntry }) => ({ request: 'launch', program, args, cwd, stopAtBeginningOfMainSubprogram: !!stopOnEntry }),
    attachArgs: ({ pid }) => ({ request: 'attach', pid }),
  },
  dlv: {
    languages: ['go'], extensions: ['.go'],
    detect: () => { const b = which('dlv'); return b ? { kind: 'tcp-server', command: b, scriptArgs: (port) => ['dap', '--listen', `127.0.0.1:${port}`] } : null },
    install: 'go install github.com/go-delve/delve/cmd/dlv@latest',
    launchArgs: ({ program, args, cwd, env, stopOnEntry }) => ({ request: 'launch', mode: program.endsWith('.go') || fs.statSync(program).isDirectory() ? 'debug' : 'exec', program, args, cwd, env, stopOnEntry: !!stopOnEntry }),
    attachArgs: ({ pid }) => ({ request: 'attach', mode: 'local', processId: pid }),
    acceptsDirectoryProgram: true,
  },
}

export function pickAdapter(program, forced) {
  if (forced) {
    if (!ADAPTERS[forced]) throw new Error(`unknown adapter ${forced}; available: ${Object.keys(ADAPTERS).join(', ')}`)
    return forced
  }
  const ext = path.extname(program ?? '').toLowerCase()
  if (['.py'].includes(ext)) return 'debugpy'
  if (['.js', '.mjs', '.cjs', '.ts', '.mts'].includes(ext)) return 'node'
  if (ext === '.go' || (program && fs.existsSync(program) && fs.statSync(program).isDirectory() && fs.existsSync(path.join(program, 'go.mod')))) return 'dlv'
  // native binary: prefer lldb-dap, then gdb
  for (const a of ['lldb-dap', 'gdb']) if (ADAPTERS[a].detect()) return a
  return 'lldb-dap'
}

export function adapterStatus() {
  return Object.entries(ADAPTERS).map(([id, a]) => ({ id, available: !!a.detect(), languages: a.languages, install: a.install }))
}

/** One debug session (root DAP connection plus any child sessions it spawns). */
export class DebugSession {
  constructor(id, adapterId) {
    this.id = id
    this.adapterId = adapterId
    this.state = 'starting'
    this.stopped = null // { reason, threadId, description, text }
    this.breakpoints = new Map() // file -> [{line, condition, hitCondition, logMessage}]
    this.functionBreakpoints = []
    this.client = null
    this.children = []
    this.exitCode = undefined
  }

  /** The client that currently owns execution (latest child with threads, else root). */
  get active() { return this.children.findLast((c) => !c.closed) ?? this.client }
}

export class SessionManager {
  constructor({ log = () => {} } = {}) {
    this.sessions = new Map()
    this.log = log
    this.seq = 0
  }

  get current() { return [...this.sessions.values()].findLast((s) => s.state !== 'terminated') }

  async connect(adapterId, cwd, { reusePort } = {}) {
    const a = ADAPTERS[adapterId]
    const spec = a.detect()
    if (!spec) throw new Error(`debug adapter ${adapterId} is not installed (${a.install}).`)
    if (spec.kind === 'stdio') return DapClient.spawnStdio(adapterId, spec.command, spec.args, { cwd })
    // Child sessions (js-debug startDebugging) connect to the parent's server, not a new one.
    if (reusePort) return DapClient.connectTcp(adapterId, { port: reusePort, cwd })
    const port = await freePort()
    const c = await DapClient.connectTcp(adapterId, { port, spawnCmd: spec.command, spawnArgs: spec.scriptArgs(port), cwd })
    c.serverPort = port
    return c
  }

  wire(session, client, root = true) {
    client.on('stopped', async (b) => {
      session.state = 'stopped'
      session.stopped = { reason: b.reason, threadId: b.threadId, description: b.description ?? b.text, allThreadsStopped: b.allThreadsStopped, hitBreakpointIds: b.hitBreakpointIds, client }
      session.activeClient = client
    })
    client.on('continued', () => { if (session.stopped?.client === client) { session.state = 'running'; session.stopped = null } })
    client.on('exited', (b) => { session.exitCode = b.exitCode })
    client.on('terminated', () => {
      if (!root) return
      session.state = 'terminated'
      // The debuggee is gone: release adapters (children first, then the server-owning root).
      setTimeout(() => { for (const c of [...session.children, session.client]) c?.close('debuggee terminated') }, 300).unref?.()
    })
    client.on('closed', () => { if (root) session.state = 'terminated' })
    // js-debug: child targets arrive as startDebugging reverse requests.
    client.reverse.startDebugging = async (args) => {
      const child = await this.connect(session.adapterId, session.cwd, { reusePort: session.client.serverPort })
      session.children.push(child)
      this.wire(session, child, false)
      await child.request('initialize', initArgs(session.adapterId))
      const launched = child.request(args.request ?? 'launch', args.configuration ?? {}, 60000)
      await this.syncBreakpoints(session, child)
      await child.request('configurationDone', {}).catch(() => {})
      await launched.catch((e) => client.log('stderr', `child ${args.request}: ${e.message}\n`))
      return {}
    }
    client.reverse.runInTerminal = async (args) => {
      const { spawn } = await import('node:child_process')
      const p = spawn(args.args[0], args.args.slice(1), { cwd: args.cwd, env: { ...process.env, ...(args.env ?? {}) }, stdio: ['ignore', 'pipe', 'pipe'], detached: false })
      p.stdout.on('data', (d) => client.log('stdout', String(d)))
      p.stderr.on('data', (d) => client.log('stderr', String(d)))
      return { processId: p.pid }
    }
  }

  async start({ request, adapter, program, args = [], cwd, env, stopOnEntry, host, port, pid, timeoutMs = 30000, breakpoints = [] }) {
    if (this.current) throw new Error(`a debug session is already active (${this.current.id}, ${this.current.adapterId}); terminate it first`)
    const adapterId = pickAdapter(program, adapter ?? (request === 'attach' && port && !pid ? 'debugpy' : undefined))
    const id = `dbg${++this.seq}`
    const s = new DebugSession(id, adapterId)
    s.cwd = cwd
    s.program = program
    for (const bp of breakpoints) {
      if (bp.function) s.functionBreakpoints.push({ name: bp.function, condition: bp.condition })
      else s.breakpoints.set(bp.file, [...(s.breakpoints.get(bp.file) ?? []).filter((b) => b.line !== bp.line), bp])
    }
    this.sessions.set(id, s)
    try {
      s.client = await this.connect(adapterId, cwd)
      this.wire(s, s.client, true)
      s.capabilities = await s.client.request('initialize', initArgs(adapterId), timeoutMs)
      const initialized = s.client.waitFor('initialized', { timeoutMs })
      const a = ADAPTERS[adapterId]
      const reqArgs = request === 'attach' ? a.attachArgs({ host, port, pid }) : a.launchArgs({ program, args, cwd, env, stopOnEntry })
      const started = s.client.request(request, reqArgs, timeoutMs * 2)
      started.catch(() => {})
      await initialized
      await this.syncBreakpoints(s, s.client)
      if (s.capabilities?.supportsConfigurationDoneRequest !== false) await s.client.request('configurationDone', {}, timeoutMs).catch(() => {})
      await started
      if (s.state === 'starting') s.state = 'running'
      return s
    } catch (e) {
      s.client?.close('start failed')
      s.state = 'terminated'
      throw e
    }
  }

  async syncBreakpoints(s, client) {
    for (const [file, bps] of s.breakpoints) {
      const r = await client.request('setBreakpoints', { source: { path: file }, breakpoints: bps.map((b) => ({ line: b.line, ...(b.condition ? { condition: b.condition } : {}), ...(b.hitCondition ? { hitCondition: b.hitCondition } : {}), ...(b.logMessage ? { logMessage: b.logMessage } : {}) })) }).catch((e) => ({ error: e.message }))
      s.lastBreakpointResult = r
    }
    if (s.functionBreakpoints.length && client.capabilities?.supportsFunctionBreakpoints !== false) {
      await client.request('setFunctionBreakpoints', { breakpoints: s.functionBreakpoints.map((f) => ({ name: f.name, ...(f.condition ? { condition: f.condition } : {}) })) }).catch(() => {})
    }
  }

  async stopAll() {
    for (const s of this.sessions.values()) {
      for (const c of [...s.children, s.client]) {
        if (!c || c.closed) continue
        await c.request('disconnect', { terminateDebuggee: true }, 3000).catch(() => {})
        c.close('terminated')
      }
      s.state = 'terminated'
    }
  }
}

export function initArgs(adapterId) {
  return {
    clientID: 'dsh-omp-debug', clientName: 'DSH omp-debug', adapterID: adapterId, locale: 'en',
    linesStartAt1: true, columnsStartAt1: true, pathFormat: 'path',
    supportsVariableType: true, supportsVariablePaging: true, supportsRunInTerminalRequest: true,
    supportsMemoryReferences: true, supportsProgressReporting: false, supportsInvalidatedEvent: true,
    supportsMemoryEvent: false, supportsStartDebuggingRequest: true, supportsArgsCanBeInterpretedByShell: false,
  }
}