/**
 * OPS110 — sessões persistentes de agente (attach/detach).
 *
 * Pura por contrato: nada aqui faz I/O além de resolver paths (o CLI
 * `scripts/agent-session.mjs` é quem spawna/HTTP). O ciclo: um `opencode serve`
 * compartilhado (loopback por padrão) é dono das sessões; cada run é dirigido
 * por um `opencode run --attach … --auto --command …` destacado (é o `--auto`
 * dele que aprova permissões enquanto o run vive) e observado por um TUI
 * `opencode attach -s <sessionID>` que pode entrar e sair à vontade — sair do
 * cliente nunca encerra o run; encerrar é `stop` (abort via API).
 *
 * O estado por run (`sessionStatePath`) é o índice de endereçamento consumido
 * pelo painel OPS109 (`list --json`): branch/dir/sessionID/url/driverPid/log.
 * Nenhuma credencial é persistida — `OPENCODE_SERVER_PASSWORD`/
 * `OPENCODE_SERVER_USERNAME` vivem só no ambiente; bind fora do loopback sem
 * senha falha fechado (`validateServerBind`).
 */
import { homedir } from 'node:os'
import { join } from 'node:path'

import { slugify } from '../../src/lib/slug.ts'

/** Default host of the shared agent server — loopback only, never `0.0.0.0`. */
export const DEFAULT_AGENT_SERVER_HOST = '127.0.0.1'

/**
 * Default port. Fora da faixa de dev dos worktrees (`3100+slot`, slot ≤ 999 →
 * até 4099) e longe dos servidores que a máquina já pode ter (4096 Zed ACP,
 * 4097 `opencode web` do usuário). `TEQO_AGENT_SERVER_PORT` overrides.
 */
export const DEFAULT_AGENT_SERVER_PORT = 4199

/** State-file schema version — `list --json` carries it for OPS109. */
export const STATE_VERSION = 1

/**
 * Resolve host/port/url for the shared server: explicit flags (`serve
 * --hostname/--port`) > env (`TEQO_AGENT_SERVER_HOST/PORT`) > defaults. Fail
 * high on a non-numeric/out-of-range port — never guess a listening address.
 * @param {{ hostname?: string | null, port?: number | string | null, env?: Record<string, string | undefined> }} [options]
 */
export const resolveServerConfig = ({ hostname = null, port = null, env = process.env } = {}) => {
  const resolvedHostname = hostname ?? env.TEQO_AGENT_SERVER_HOST ?? DEFAULT_AGENT_SERVER_HOST
  const rawPort = port ?? env.TEQO_AGENT_SERVER_PORT ?? DEFAULT_AGENT_SERVER_PORT
  const resolvedPort = Number(rawPort)
  if (!Number.isInteger(resolvedPort) || resolvedPort < 1 || resolvedPort > 65535) {
    throw new Error(`porta inválida para o servidor de sessões: ${rawPort}`)
  }
  return {
    hostname: resolvedHostname,
    port: resolvedPort,
    url: `http://${resolvedHostname}:${resolvedPort}`,
  }
}

/**
 * Loopback spellings only — `0.0.0.0`, hostnames that merely START with `127.`
 * (`127.0.0.1.example.com`) and any routable address are NOT loopback.
 */
export const isLoopbackHost = (hostname) => {
  const host = String(hostname ?? '')
    .trim()
    .toLowerCase()
    .replace(/^\[|\]$/g, '')
  if (host === 'localhost' || host === '::1') return true
  return /^127(\.\d{1,3}){3}$/.test(host)
}

/**
 * Fail-closed bind policy: anything beyond loopback requires the opencode
 * server credential (`OPENCODE_SERVER_PASSWORD`); loopback may run without it.
 * Returns true on success so callers can gate the spawn on the exception.
 */
export const validateServerBind = ({ hostname, password }) => {
  if (isLoopbackHost(hostname)) return true
  if (typeof password === 'string' && password.length > 0) return true
  throw new Error(
    `bind em ${hostname} exige credencial: defina OPENCODE_SERVER_PASSWORD (fail-closed fora do loopback)`,
  )
}

/**
 * State dir: `TEQO_AGENT_SESSION_DIR` > `$XDG_STATE_HOME/teqo/agent-sessions` >
 * `~/.local/state/teqo/agent-sessions`.
 * @param {Record<string, string | undefined>} [env]
 */
export const sessionDirFromEnv = (env = process.env) => {
  if (env.TEQO_AGENT_SESSION_DIR) return env.TEQO_AGENT_SESSION_DIR
  const stateHome = env.XDG_STATE_HOME || join(env.HOME || homedir(), '.local', 'state')
  return join(stateHome, 'teqo', 'agent-sessions')
}

/** One filename-safe key per branch — `plans/plan-issue-1` → `plans-plan-issue-1`. */
export const sessionSlug = (branch) => slugify(String(branch ?? ''))

/** `<code>-<slug>` claim branch → code; namespace branches (`plans/`, `work/`, `fix/`) → null. */
export const codeFromBranch = (branch) => {
  const match = /^([A-Z][A-Za-z0-9]*)-/.exec(String(branch ?? ''))
  return match ? match[1] : null
}

export const sessionStatePath = ({ sessionDir, branch }) =>
  join(sessionDir, `${sessionSlug(branch)}.json`)

export const serverStatePath = ({ sessionDir }) => join(sessionDir, 'server.json')

export const startLockPath = ({ sessionDir, branch }) =>
  join(sessionDir, `${sessionSlug(branch)}.lock`)

export const driverLogPath = ({ sessionDir, branch }) =>
  join(sessionDir, `${sessionSlug(branch)}.log`)

const assertSessionState = (state) => {
  const invalid = (reason) => {
    throw new Error(`estado de sessão inválido: ${reason}`)
  }
  if (!state || typeof state !== 'object' || Array.isArray(state)) invalid('não é objeto')
  if (!Number.isInteger(state.version) || state.version < 1) invalid('version')
  if (typeof state.sessionID !== 'string' || !state.sessionID.startsWith('ses'))
    invalid('sessionID')
  if (typeof state.branch !== 'string' || state.branch.length === 0) invalid('branch')
  if (typeof state.dir !== 'string' || state.dir.length === 0) invalid('dir')
  if (typeof state.url !== 'string' || !state.url.startsWith('http')) invalid('url')
  return state
}

export const serializeSessionState = (state) =>
  `${JSON.stringify(assertSessionState(state), null, 2)}\n`

export const parseSessionState = (text) => {
  let parsed
  try {
    parsed = JSON.parse(text)
  } catch {
    throw new Error('estado de sessão inválido: JSON ilegível')
  }
  return assertSessionState(parsed)
}

const assertServerState = (state) => {
  const invalid = (reason) => {
    throw new Error(`estado do servidor inválido: ${reason}`)
  }
  if (!state || typeof state !== 'object' || Array.isArray(state)) invalid('não é objeto')
  if (typeof state.url !== 'string' || !state.url.startsWith('http')) invalid('url')
  if (!Number.isInteger(state.port)) invalid('port')
  if (!Number.isInteger(state.pid) || state.pid <= 0) invalid('pid')
  return state
}

export const serializeServerState = (state) =>
  `${JSON.stringify(assertServerState(state), null, 2)}\n`

export const parseServerState = (text) => {
  let parsed
  try {
    parsed = JSON.parse(text)
  } catch {
    throw new Error('estado do servidor inválido: JSON ilegível')
  }
  return assertServerState(parsed)
}

/**
 * Skill command per launch purpose — the terminal launch auto-submits it on
 * the server-owned session. `new` deliberately has none ("apenas conversar");
 * `plan` only submits `/plan-issue` when a bag (the opening message) is given,
 * otherwise it is driverless like `new` so the human can type the context.
 */
export const SESSION_COMMAND_BY_PURPOSE = {
  next: 'work-issue',
  plan: 'plan-issue',
  new: null,
  fix: 'bug-fix',
}

/**
 * `{ command, arguments }` for the purpose, or null when there is nothing to
 * auto-submit. `next` carries only a valid claimed issue (`--issue N`); `fix`
 * and `plan` carry the sanitized bag (quotes/backslashes stripped — the value
 * rides a single argv token). `fix` with an empty bag still submits the bare
 * `/bug-fix`; `plan` with an empty bag is driverless by design (no context to
 * plan with — mirrors `new`). Unknown purposes degrade to no command
 * (fail-safe, mirrors the old directive).
 *
 * `auto` (OPS122) is the HUMAN's skill flag (`--auto` on the launcher line),
 * NEVER the `opencode run --auto` permission flag that `driverArgs` emits on
 * its own. When true it transposes into the skill text exactly as documented:
 * `/work-issue --issue <N> --auto`, `/plan-issue --auto <bag>`,
 * `/bug-fix --auto <bag>` (bare `/bug-fix --auto` with an empty bag). It is a
 * text argument, not an argv flag, because the skill parses it from its
 * invocation.
 * @param {{ purpose?: string, issueNumber?: number | string | null, argument?: string | null, auto?: boolean }} [options]
 */
export const purposeInvocation = ({
  purpose = null,
  issueNumber = null,
  argument = null,
  auto = false,
} = {}) => {
  const command = SESSION_COMMAND_BY_PURPOSE[purpose] ?? null
  if (!command) return null
  if (purpose === 'next') {
    const number = Number(issueNumber)
    if (!Number.isInteger(number) || number <= 0) return null
    return { command, arguments: `--issue ${number}${auto ? ' --auto' : ''}` }
  }
  if (purpose === 'fix' || purpose === 'plan') {
    // Mesma sanitização da diretiva de launch (fronteira dupla de propósito:
    // o xargs da camada shell e o argv do `opencode run` não honram escapes).
    const sanitized = typeof argument === 'string' ? argument.replace(/["\\]/g, '').trim() : ''
    if (purpose === 'plan' && !sanitized) return null
    if (auto) return { command, arguments: sanitized ? `--auto ${sanitized}` : '--auto' }
    return { command, arguments: sanitized }
  }
  return { command, arguments: '' }
}

/**
 * Split a `provider/model` string (the format of `WORKTREE_MODEL_MAP` and the
 * opencode `--model` flag) into the `{ providerID, id }` pair the server's
 * `POST /session` expects. The split is on the FIRST slash: model ids may
 * themselves carry slashes (`openrouter/openrouter/free`). Fail high on a
 * string without both halves — never send the server a half ref.
 * @param {string} model
 */
export const parseModelRef = (model) => {
  if (typeof model !== 'string' || model.length === 0) {
    throw new Error('parseModelRef: model ausente')
  }
  const slash = model.indexOf('/')
  if (slash <= 0 || slash === model.length - 1) {
    throw new Error(`parseModelRef: modelo inválido "${model}" (esperado provider/model)`)
  }
  return { providerID: model.slice(0, slash), id: model.slice(slash + 1) }
}

/**
 * Body of `POST /session` — `{}` when no model was requested, or
 * `{ model: { providerID, id } }` when one was (the session then reports the
 * model, so the attached TUI inherits it even on a driverless launch). No
 * `variant` (OPS95: variants stay on the machine's global config).
 * @param {{ model?: string | null }} [options]
 */
export const buildCreateSessionBody = ({ model = null } = {}) => {
  if (model === null || model === undefined || model === '') return {}
  return { model: parseModelRef(model) }
}

/**
 * Internal `start` argv flag carrying the HUMAN's skill `--auto` (opt-out of the
 * skill GATE) — deliberately distinct from the `opencode run --auto` permission
 * flag `driverArgs` emits. Single owner of the name: the worktree launch
 * directive, the session allowlist and the CLI all use this constant.
 */
export const SKILL_AUTO_FLAG = 'skill-auto'

/**
 * Accepted flag NAMES per subcommand (OPS110-F1). Names only — the `=`/boolean
 * form stays `parseEqualsFlags`' concern. `list`/`start`/`serve` legitimately
 * take `--hostname/--port` (they override the probe/spawn target). An unknown
 * name must fail high: `--prupose=next` used to fall through to the `new`
 * default and create a driverless session.
 */
export const SESSION_FLAG_ALLOWLIST = {
  serve: ['hostname', 'port'],
  start: [
    'purpose',
    'dir',
    'model',
    'issue',
    'argument',
    'new',
    SKILL_AUTO_FLAG,
    'hostname',
    'port',
  ],
  attach: ['session', 'branch', 'issue'],
  stop: ['session', 'branch', 'issue'],
  list: ['json', 'hostname', 'port'],
}

/** Optimal string alignment (Damerau–Levenshtein, no adjacent transposition twice). */
const osaDistance = (left, right) => {
  const a = String(left ?? '')
  const b = String(right ?? '')
  if (a === b) return 0
  if (a.length === 0) return b.length
  if (b.length === 0) return a.length
  const rows = Array.from({ length: a.length + 1 }, () => new Array(b.length + 1).fill(0))
  for (let i = 0; i <= a.length; i += 1) rows[i][0] = i
  for (let j = 0; j <= b.length; j += 1) rows[0][j] = j
  for (let i = 1; i <= a.length; i += 1) {
    for (let j = 1; j <= b.length; j += 1) {
      const cost = a[i - 1] === b[j - 1] ? 0 : 1
      rows[i][j] = Math.min(rows[i - 1][j] + 1, rows[i][j - 1] + 1, rows[i - 1][j - 1] + cost)
      if (i > 1 && j > 1 && a[i - 1] === b[j - 2] && a[i - 2] === b[j - 1]) {
        rows[i][j] = Math.min(rows[i][j], rows[i - 2][j - 2] + 1)
      }
    }
  }
  return rows[a.length][b.length]
}

/**
 * Closest accepted flag at edit distance ≤1, or null. Damerau (transposition
 * counts as 1) so the required `--prupose` → `--purpose` suggestion fires;
 * limiar estrito evita sugerir em erros grandes (ruído acionável falso).
 * @param {string} name
 * @param {readonly string[]} accepted
 */
export const nearestAcceptedFlag = (name, accepted) => {
  let best = null
  let bestDistance = Number.POSITIVE_INFINITY
  for (const candidate of accepted) {
    const distance = osaDistance(name, candidate)
    if (distance < bestDistance || (distance === bestDistance && candidate < String(best))) {
      best = candidate
      bestDistance = distance
    }
  }
  return bestDistance <= 1 ? best : null
}

/**
 * Fail high on any flag the subcommand does not accept. Throws a message with
 * a suggestion when a near neighbor exists; unknown subcommands return silently
 * (the CLI prints the USAGE for those). A bare `--` parses to an empty name and
 * is ignored, not reported as a typo.
 *
 * Single owner of the fail-high message: both the session CLI
 * (`validateSessionFlags`) and the worktree launcher (`validateWorktreeFlags`)
 * delegate here, so the wording and the suggestion rule never drift.
 * @param {{ flags?: Record<string, unknown>, accepted?: readonly string[] }} [options]
 */
export const assertKnownFlags = ({ flags = {}, accepted = [] } = {}) => {
  for (const name of Object.keys(flags)) {
    if (name === '' || accepted.includes(name)) continue
    const suggestion = nearestAcceptedFlag(name, accepted)
    throw new Error(
      suggestion
        ? `flag desconhecida: --${name} (sugestão: --${suggestion}).`
        : `flag desconhecida: --${name}.`,
    )
  }
}

/**
 * Fail high on any flag the subcommand does not accept (names only — the
 * `=`/boolean form stays `parseEqualsFlags`' concern). Unknown subcommands
 * return silently (the CLI prints the USAGE for those).
 * @param {{ subcommand?: string | null, flags?: Record<string, unknown> }} [options]
 */
export const validateSessionFlags = ({ subcommand = null, flags = {} } = {}) => {
  const accepted = SESSION_FLAG_ALLOWLIST[subcommand]
  if (!accepted) return
  assertKnownFlags({ flags, accepted })
}

/**
 * argv of the detached run driver (sem o binário — o caller usa
 * `spawn('opencode', …)`). The `--` separator is required so a command
 * argument starting with `-` (`--issue 1019`) is not parsed as an opencode flag
 * by yargs — verified live on 1.18.31. No `-p`: the credential rides
 * `OPENCODE_SERVER_PASSWORD` in the inherited env (never in `ps`).
 * @param {{ url: string, sessionID: string, dir: string, model: string, invocation: { command: string, arguments?: string } | null }} options
 */
export const driverArgs = ({ url, sessionID, dir, model, invocation }) => {
  if (typeof url !== 'string' || url.length === 0) throw new Error('driverArgs: url ausente')
  if (typeof sessionID !== 'string' || sessionID.length === 0) {
    throw new Error('driverArgs: session ausente')
  }
  if (typeof dir !== 'string' || dir.length === 0) throw new Error('driverArgs: dir ausente')
  if (typeof model !== 'string' || model.length === 0) throw new Error('driverArgs: model ausente')
  if (!invocation || typeof invocation.command !== 'string' || invocation.command.length === 0) {
    throw new Error('driverArgs: invocation/comando ausente')
  }
  const argv = [
    'run',
    '--attach',
    url,
    '-s',
    sessionID,
    '--dir',
    dir,
    '--model',
    model,
    '--auto',
    '--command',
    invocation.command,
  ]
  if (invocation.arguments) argv.push('--', invocation.arguments)
  return argv
}

/**
 * Args do TUI anexado, SEM o binário (`opencode attach` não tem
 * `--auto`/`--model` por design; o caller usa `spawn('opencode', …)`).
 */
export const attachArgs = ({ url, sessionID, dir }) => {
  if (typeof url !== 'string' || url.length === 0) throw new Error('attachArgs: url ausente')
  if (typeof sessionID !== 'string' || sessionID.length === 0) {
    throw new Error('attachArgs: session ausente')
  }
  if (typeof dir !== 'string' || dir.length === 0) throw new Error('attachArgs: dir ausente')
  return ['attach', url, '--dir', dir, '-s', sessionID]
}

/** Args do servidor headless, SEM o binário. Nunca `--mdns` (anunciaria na rede). */
export const serverArgs = ({ port, hostname }) => {
  if (!Number.isInteger(port)) throw new Error('serverArgs: porta inválida')
  if (typeof hostname !== 'string' || hostname.length === 0) {
    throw new Error('serverArgs: hostname ausente')
  }
  return ['serve', '--port', String(port), '--hostname', hostname]
}

/**
 * Pick the state a command refers to — `--session` > `--branch` > `--issue` >
 * the current branch. Null when nothing matches (callers print the known refs).
 * @param {{ states: Array<Record<string, unknown>>, session?: string | null, branch?: string | null, issue?: number | string | null, cwdBranch?: string | null }} options
 */
export const resolveSessionRef = ({
  states,
  session = null,
  branch = null,
  issue = null,
  cwdBranch = null,
}) => {
  const list = Array.isArray(states) ? states : []
  if (session) {
    const hit = list.find((state) => state.sessionID === session)
    if (hit) return hit
  }
  if (branch) {
    const hit = list.find((state) => state.branch === branch)
    if (hit) return hit
  }
  const number = issue === null || issue === '' ? null : Number(issue)
  if (Number.isInteger(number) && number > 0) {
    const hit = list.find((state) => state.issue === number)
    if (hit) return hit
  }
  if (cwdBranch) {
    const hit = list.find((state) => state.branch === cwdBranch)
    if (hit) return hit
  }
  return null
}

/**
 * Decide "reuse the existing run vs create a fresh one" — the single-flight
 * invariant's brain (OPS110-F1). Pure: the caller injects the filesystem read,
 * the busy probe and the driver liveness check. Mirrors `cmdStart`'s in-lock
 * decision: `--new`/no state/unreadable state/different server → fresh; an
 * alive driver or a busy session on the SAME server → reuse. `reason` lets the
 * CLI keep its "estado ilegível" warning without the lib doing I/O.
 * @param {{
 *   forceNew?: boolean,
 *   statePath: string,
 *   readFile: (path: string) => string,
 *   exists: (path: string) => boolean,
 *   parse?: (text: string) => Record<string, unknown>,
 *   serverUrl: string,
 *   probeBusy: (sessionID: string) => boolean | Promise<boolean>,
 *   driverAlive?: (pid: number | null, sessionID: string | null) => boolean,
 * }} options
 * @returns {Promise<{ action: 'reuse' | 'fresh', reason: 'forced' | 'missing' | 'unreadable' | 'server-mismatch' | 'running' | 'idle', state?: Record<string, unknown>, error?: Error }>}
 */
export const resolveStartDecision = async ({
  forceNew = false,
  statePath,
  readFile,
  exists,
  parse = parseSessionState,
  serverUrl,
  probeBusy,
  driverAlive = () => false,
}) => {
  if (forceNew) return { action: 'fresh', reason: 'forced' }
  if (!exists(statePath)) return { action: 'fresh', reason: 'missing' }
  let existing
  try {
    existing = parse(readFile(statePath))
  } catch (error) {
    return { action: 'fresh', reason: 'unreadable', error }
  }
  if (existing.url !== serverUrl) return { action: 'fresh', reason: 'server-mismatch' }
  const busy = Boolean(await probeBusy(existing.sessionID))
  if (driverAlive(existing.driverPid, existing.sessionID) || busy) {
    return { action: 'reuse', reason: 'running', state: existing }
  }
  return { action: 'fresh', reason: 'idle' }
}

/**
 * Whether an existing start-lock's holder is gone and the lock can be
 * reclaimed. Pure: PID liveness is injected. A missing/non-numeric/dead holder
 * counts as stale — the same branch the CLI used to inline.
 * @param {{ holderPid?: number | string | null, isPidAlive: (pid: number) => boolean }} options
 */
export const isStaleLock = ({ holderPid, isPidAlive }) => {
  const pid = Number(holderPid)
  if (!Number.isInteger(pid) || pid <= 0) return true
  return !isPidAlive(pid)
}

/**
 * Status shown by `list`: `stopped` (explicit stop) wins, then `unknown`
 * (server unreachable), then `working` (busy on the server or driver alive),
 * else `idle`.
 */
export const deriveSessionStatus = ({ state, serverHealthy, sessionBusy, driverAlive }) => {
  if (state?.stoppedAt) return 'stopped'
  if (!serverHealthy) return 'unknown'
  if (sessionBusy || driverAlive) return 'working'
  return 'idle'
}

/**
 * Versioned machine contract of `list --json` (OPS109 consumes it):
 * `{ version, server, sessions: [{...state, status}] }`.
 */
export const sessionListPayload = ({ states, statuses = {}, server }) => ({
  version: STATE_VERSION,
  server,
  sessions: (Array.isArray(states) ? states : []).map((state) => ({
    ...state,
    status: statuses[state.sessionID] ?? 'unknown',
  })),
})

/** Human `list` lines — status first, `—` for namespace runs; `logPath` last. */
export const formatSessionList = (rows) =>
  (Array.isArray(rows) ? rows : []).map((row) => {
    const reference =
      [row.code, row.issue ? `#${row.issue}` : null].filter(Boolean).join(' ') || '—'
    return `${String(row.status).padEnd(8)} ${reference}  ${row.sessionID}  ${row.branch}  ${row.dir}  ${row.logPath ?? '—'}`
  })