/**
 * Locating, installing, and invoking the slopo CLI.
 *
 * Everything here is a pure function of its arguments so the decisions can be
 * tested without a running harness. The one side effect — running `uv` — is
 * expressed as a command line that the caller executes through the shell seam.
 *
 * Slopo is driven as a separate process, never imported. Its package is
 * AGPL-3.0-or-later and the README does not accept patches, so the command-line
 * interface is the only contract worth building on.
 */

import { existsSync } from 'node:fs'
import { delimiter, join } from 'node:path'
import { managedPythonDir, managedSlopoPath, managedToolDir, userLocalSlopoPath } from './paths.js'

/** The PyPI distribution name. */
export const SLOPO_PACKAGE = 'slopo'

/** Slopo requires Python >= 3.12; uv fetches a managed interpreter for this. */
export const SLOPO_PYTHON = '3.12'

/**
 * The agent-config version this bundle's ported skills were written against.
 *
 * Slopo's `--config-version` flag fails the command when the agent-facing
 * contract has moved on, which is the signal that the skill text in `skills/`
 * is stale and needs re-porting. Passing it is therefore a deliberate alarm,
 * not boilerplate.
 */
export const SLOPO_AGENT_CONFIG_VERSION = 1

const EXE = process.platform === 'win32' ? 'slopo.exe' : 'slopo'

/**
 * Binaries to try, best first.
 *
 * The managed install is checked before `PATH`, because a stale slopo of a
 * different version earlier on `PATH` would otherwise silently win.
 *
 * @param {string} dshHome
 * @param {Record<string, string | undefined>} [env]
 * @returns {string[]}
 */
export function slopoCandidates(dshHome, env = process.env) {
  const candidates = []
  const configured = typeof env.DSH_SLOPO_BINARY === 'string' ? env.DSH_SLOPO_BINARY.trim() : ''
  if (configured !== '') candidates.push(configured)
  candidates.push(managedSlopoPath(dshHome))
  for (const dir of (env.PATH ?? '').split(delimiter)) {
    if (dir !== '') candidates.push(join(dir, EXE))
  }
  candidates.push(userLocalSlopoPath(env))
  return candidates
}

/**
 * The first candidate that exists, or `undefined`.
 *
 * @param {string} dshHome
 * @param {Record<string, string | undefined>} [env]
 * @param {(path: string) => boolean} [exists] injected for tests
 * @returns {string | undefined}
 */
export function findSlopo(dshHome, env = process.env, exists = existsSync) {
  for (const candidate of slopoCandidates(dshHome, env)) {
    if (exists(candidate)) return candidate
  }
  return undefined
}

/**
 * The environment `uv` must run under to install into `$DSH_HOME`.
 *
 * All three variables are redirected: `UV_TOOL_DIR` for the venv and shim,
 * `UV_TOOL_BIN_DIR` for the executable, and `UV_PYTHON_INSTALL_DIR` for the
 * CPython that slopo requires. Without the last one uv downloads a second
 * interpreter into the container's writable layer and the install does not
 * survive a container recreation.
 *
 * @param {string} dshHome
 * @param {Record<string, string | undefined>} [env]
 * @returns {Record<string, string | undefined>}
 */
export function installEnv(dshHome, env = process.env) {
  return {
    ...env,
    UV_TOOL_DIR: managedToolDir(dshHome),
    UV_TOOL_BIN_DIR: join(managedToolDir(dshHome), 'bin'),
    UV_PYTHON_INSTALL_DIR: managedPythonDir(dshHome),
  }
}

/**
 * The `uv` arguments that install or upgrade slopo into `$DSH_HOME`.
 *
 * @param {{ upgrade?: boolean, version?: string }} [options]
 * @returns {string[]}
 */
export function uvInstallArgs({ upgrade = false, version = '' } = {}) {
  const spec = version === '' ? SLOPO_PACKAGE : `${SLOPO_PACKAGE}==${version.replace(/^v/, '')}`
  return ['tool', 'install', spec, '--python', SLOPO_PYTHON, ...(upgrade ? ['--upgrade'] : [])]
}

/** POSIX single-quote a value. The harness shell is `bash -c` on this platform. */
export function shellQuote(value) {
  return `'${String(value).replace(/'/g, `'\\''`)}'`
}

/** Join argv into a command line the shell seam can execute. */
export function commandLine(argv) {
  return argv.map(shellQuote).join(' ')
}

/**
 * Slopo arguments for one action.
 *
 * `--config` is a global option on slopo's Typer callback, so it must precede
 * the subcommand. That placement was verified against slopo 0.8.0 rather than
 * assumed.
 *
 * @param {string} configPath
 * @param {string} action
 * @param {{ base?: string, cluster?: string }} [params]
 * @returns {string[]}
 */
export function slopoArgs(configPath, action, params = {}) {
  const global = ['--config', configPath]
  const version = ['--config-version', String(SLOPO_AGENT_CONFIG_VERSION)]
  const bare = ['--config', configPath]
  switch (action) {
    case 'review': {
      const args = [...global, 'agent-review', ...version]
      if (params.base !== undefined && params.base !== '') args.push('--base', params.base)
      return args
    }
    case 'analyze':
      return [...global, 'agent-analyze', ...version]
    case 'analyze-one': {
      const args = [...global, 'agent-analyze', ...version, '--single']
      if (params.cluster !== undefined && params.cluster !== '') args.push('--cluster', params.cluster)
      return args
    }
    case 'index':
      return [...bare, 'index']
    case 'embed':
      return [...bare, 'embed']
    case 'show-config':
      return [...bare, 'show-config']
    case 'version':
      return ['--version']
    default:
      throw new Error(`unknown slopo action "${action}"`)
  }
}

/**
 * Turn slopo's deliberately terse agent-facing failure into something the model
 * can act on.
 *
 * Slopo prints a short non-revealing line on stderr and writes the real detail
 * to the agent log, so a bare relay of stderr leaves the agent with no move. Each
 * mapping below was produced by actually triggering the failure against slopo
 * 0.8.0, not by reading its error table.
 *
 * @param {{ stderr: string, stdout: string, logDetail?: string }} input
 * @returns {{ code: string, message: string, remedy: string }}
 */
export function explainFailure({ stderr, stdout, logDetail = '' }) {
  const text = `${stderr}\n${stdout}\n${logDetail}`
  if (/No data in database/i.test(text)) {
    return {
      code: 'DATABASE_MISSING',
      message: 'slopo has no index for this workspace yet.',
      remedy:
        'Run the `slopo` tool with action "prepare" first. It runs `slopo index`, which is local ' +
        'parsing and costs nothing, and then embeds. A review cannot bootstrap the database itself.',
    }
  }
  if (/Configuration mismatch/i.test(text)) {
    return {
      code: 'CONFIGURATION_MISMATCH',
      message:
        'The embedding model, its dimensions, the source directory, or a node-count threshold has ' +
        'changed since this workspace was first indexed.',
      remedy:
        'Slopo freezes those five values into the database and refuses to mix generations. Delete ' +
        'the database file and run "prepare" again; the next embed costs whatever embedding costs ' +
        'on the configured backend, because every unit must be re-embedded.',
    }
  }
  if (/Too many code units to embed/i.test(text)) {
    return {
      code: 'BACKLOG_TOO_LARGE',
      message:
        'More than 1000 units are unembedded. Slopo refuses to do that inside an agent call to ' +
        'protect your latency.',
      remedy:
        'Run the `slopo` tool with action "prepare" in the background. That is the same work, just ' +
        'somewhere you can watch it and cancel it.',
    }
  }
  if (/Configuration file not found/i.test(text)) {
    return {
      code: 'CONFIG_MISSING',
      message: 'The generated slopo config is missing, or the configured source directory is not a directory.',
      remedy: 'Run the `slopo` tool with action "status" to see which settings are unset, then "configure".',
    }
  }
  if (/Loading configuration failed/i.test(text)) {
    return {
      code: 'CONFIG_INVALID',
      message: 'Slopo rejected the generated config file.',
      remedy:
        'This is a bug in this plugin rather than a problem with your settings — the file is written ' +
        'from a closed allow-list. The config path and the parser error are in the detail above.',
    }
  }
  if (/Index is out of date/i.test(text)) {
    return {
      code: 'INDEX_STALE',
      message: 'The index predates the current source tree.',
      remedy: 'Run the `slopo` tool with action "prepare" to re-index and re-embed.',
    }
  }
  if (/Git command failed/i.test(text)) {
    return {
      code: 'GIT_FAILED',
      message: 'Slopo shells out to git for a review, and git failed or is missing.',
      remedy: 'Check that the workspace is a git repository and that git is installed and on PATH.',
    }
  }
  if (/Embedding failed/i.test(text)) {
    return {
      code: 'EMBEDDING_FAILED',
      message: 'The embedding backend rejected the request.',
      remedy:
        'Check the embedding model, dimensions and api_base in the settings namespace. The provider ' +
        'error itself is in the agent log, not on stdout — read it from the log file named above.',
    }
  }
  return {
    code: 'SLOPO_FAILED',
    message: 'Slopo exited non-zero and its message did not match a known failure.',
    remedy: 'Read the agent log file named above; it carries the full error, while stdout is deliberately terse.',
  }
}

/**
 * Pull the last error line out of a slopo agent log.
 *
 * Slopo writes the human-readable error to the log and only a short agent-facing
 * line to stderr, so the log is where the actionable text lives. Observed on a
 * real failure: stderr said `Embedding failed.` while the log named the exact
 * litellm parameter that was rejected.
 *
 * @param {string} contents
 * @returns {string}
 */
export function lastLogError(contents) {
  const lines = String(contents).split('\n')
  for (let index = lines.length - 1; index >= 0; index -= 1) {
    const line = lines[index].trim()
    if (line.startsWith('Error:')) return line
  }
  return ''
}