/**
 * Building the `slopo.conf.yaml` that slopo is actually invoked with.
 *
 * Two facts about slopo's config handling shape everything here.
 *
 * 1. Unknown keys are a *hard error*, not a warning (`unrecognized config key
 *    'x'`, exit 1). So this module writes from a closed allow-list and refuses
 *    to emit anything outside it.
 * 2. Relative paths resolve against the process working directory, never
 *    against the config file's own directory. So every path written here is
 *    absolute, computed by the caller.
 *
 * The embedding API key is deliberately *not* written to this file. Slopo reads
 * `SLOPO_EMBEDDING_API_KEY` from the environment *before* the YAML value, so
 * passing it in the child process's environment is both higher-precedence and
 * keeps the secret out of a file on disk.
 */

/**
 * Every key slopo 0.8.0 accepts, copied from its `_KNOWN_CONFIG_KEYS`.
 *
 * Kept as a literal rather than derived so that a slopo upgrade which adds a
 * key is a deliberate edit here instead of a silent pass-through that only
 * fails on the machine that has the newer slopo.
 */
export const SLOPO_CONFIG_KEYS = Object.freeze([
  'source_dir',
  'source_dir_exclude',
  'db_file',
  'report_dir',
  'ignore_file',
  'agent_log_file',
  'embedding_model',
  'embedding_dimensions',
  'embedding_api_key',
  'embedding_params',
  'embedding_batch_size',
  'embedding_batch_chars',
  'embedding_request_delay',
  'analyze_similarity_threshold',
  'analyze_rerank_threshold',
  'review_similarity_threshold',
  'review_rerank_threshold',
  'body_node_count_threshold',
  'block_node_count_threshold',
])

/** The three keys slopo refuses to start without. */
export const SLOPO_REQUIRED_KEYS = Object.freeze([
  'source_dir',
  'embedding_model',
  'embedding_dimensions',
])

/** Five keys slopo freezes into the database at first `index`. */
export const SLOPO_FROZEN_KEYS = Object.freeze([
  'source_dir',
  'embedding_model',
  'embedding_dimensions',
  'body_node_count_threshold',
  'block_node_count_threshold',
])

const NUMERIC_KEYS = new Set([
  'embedding_dimensions',
  'embedding_batch_size',
  'embedding_batch_chars',
  'embedding_request_delay',
  'analyze_similarity_threshold',
  'analyze_rerank_threshold',
  'review_similarity_threshold',
  'review_rerank_threshold',
  'body_node_count_threshold',
  'block_node_count_threshold',
])

/**
 * Drop empty values so an unset field falls back to slopo's own default rather
 * than being written as an empty string, which slopo rejects.
 *
 * @param {Record<string, unknown>} input
 * @returns {Record<string, unknown>} only the keys with a usable value
 */
export function pruneConfig(input) {
  const output = {}
  for (const key of SLOPO_CONFIG_KEYS) {
    if (!Object.hasOwn(input, key)) continue
    const value = input[key]
    if (value === undefined || value === null || value === '') continue
    if (Array.isArray(value) && value.length === 0) continue
    if (typeof value === 'object' && !Array.isArray(value) && Object.keys(value).length === 0) continue
    output[key] = value
  }
  return output
}

/**
 * Which required settings are still missing, so the tool can say what to do
 * rather than relaying slopo's terser message.
 *
 * @param {Record<string, unknown>} config
 * @returns {string[]} the missing key names, in slopo's own order
 */
export function missingRequired(config) {
  return SLOPO_REQUIRED_KEYS.filter((key) => {
    const value = config[key]
    return value === undefined || value === null || value === ''
  })
}

function yamlScalar(value) {
  if (typeof value === 'number') {
    if (!Number.isFinite(value)) throw new TypeError(`cannot write non-finite number to config: ${value}`)
    return String(value)
  }
  if (typeof value === 'boolean') return value ? 'true' : 'false'
  if (value === null) return 'null'
  if (typeof value !== 'string') throw new TypeError(`unsupported config value type: ${typeof value}`)
  // Always double-quoted. A path can contain spaces, colons, '#' or a leading
  // '-'/'*', each of which changes meaning in a plain scalar. Escaping is the
  // two sequences YAML's double-quoted style defines.
  return `"${value.replace(/\\/g, '\\\\').replace(/"/g, '\\"')}"`
}

function yamlBlock(key, value, lines) {
  if (Array.isArray(value)) {
    lines.push(`${key}:`)
    for (const item of value) lines.push(`  - ${yamlScalar(item)}`)
    return
  }
  if (typeof value === 'object') {
    lines.push(`${key}:`)
    for (const [nested, nestedValue] of Object.entries(value)) {
      if (nestedValue === undefined || nestedValue === null || nestedValue === '') continue
      lines.push(`  ${nested}: ${yamlScalar(nestedValue)}`)
    }
    return
  }
  lines.push(`${key}: ${yamlScalar(value)}`)
}

/**
 * Render a slopo config file.
 *
 * Emits `key: value` with a space after the colon throughout, because slopo
 * lints for exactly that and reports `missing space after ':'` otherwise.
 *
 * @param {Record<string, unknown>} config
 * @returns {string} the file contents
 */
export function renderSlopoConfig(config) {
  const pruned = pruneConfig(config)
  const lines = [
    '# Generated by dsh-slopo. Edits here are overwritten on the next run.',
    '# Change the values in the dsh-slopo settings namespace instead.',
    '#',
    '# Paths are absolute on purpose: slopo resolves relative paths against the',
    '# process working directory, not against this file.',
    '#',
    '# The embedding API key is not stored here. It is passed to slopo as the',
    '# SLOPO_EMBEDDING_API_KEY environment variable, which takes precedence over',
    '# this file anyway.',
    '',
  ]
  for (const key of SLOPO_CONFIG_KEYS) {
    if (!Object.hasOwn(pruned, key)) continue
    yamlBlock(key, pruned[key], lines)
  }
  return `${lines.join('\n')}\n`
}

/**
 * Coerce and validate the handful of values that come from a settings form, so
 * a string `"768"` typed into a text field becomes the number slopo needs.
 *
 * @param {Record<string, unknown>} input
 * @returns {{ config: Record<string, unknown>, problems: string[] }}
 */
export function normalizeConfig(input) {
  const config = pruneConfig(input)
  const problems = []
  for (const [key, value] of Object.entries(config)) {
    if (!NUMERIC_KEYS.has(key)) continue
    const numeric = typeof value === 'string' ? Number(value) : value
    if (typeof numeric !== 'number' || !Number.isFinite(numeric)) {
      problems.push(`${key} must be a number (got ${JSON.stringify(value)})`)
      delete config[key]
      continue
    }
    if (!Number.isInteger(numeric) && Number.isInteger(Number(value)) === false && key !== 'analyze_similarity_threshold') {
      // thresholds are floats; the rest are counts and a float here almost
      // always means a unit mistake
      if (!key.endsWith('_threshold')) {
        problems.push(`${key} must be a whole number (got ${numeric})`)
        delete config[key]
        continue
      }
    }
    config[key] = numeric
  }
  return { config, problems }
}