harn-stdlib 0.10.19

Embedded Harn standard library source catalog
Documentation
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/*
 * std/edit - pure helpers for applying and validating agent-authored text patches.
 */
import { edit_patch_content_hash } from "std/edit/internal"

fn __edit_collapse_ws(text) {
  return trim(regex_replace("\\s+", " ", text ?? ""))
}

fn __edit_normalize_line(line) {
  return __edit_collapse_ws(line)
}

fn __edit_structural_line(line) {
  const compact = __edit_collapse_ws(line)
  return regex_replace("\\s+", "", compact)
}

fn __edit_signature(text, structural) {
  let lines = []
  for line in split(text ?? "", "\n") {
    const normalized = if structural {
      __edit_structural_line(line)
    } else {
      __edit_normalize_line(line)
    }
    if structural && normalized == "" {
      continue
    }
    lines = lines + [normalized]
  }
  return join(lines, "\n")
}

fn __edit_nonblank_count(lines) {
  let count = 0
  for line in lines {
    if __edit_structural_line(line) != "" {
      count = count + 1
    }
  }
  return count
}

fn __edit_start_line(prefix) {
  if prefix == "" {
    return 0
  }
  return len(split(prefix, "\n")) - 1
}

fn __edit_region(start_line, end_line_exclusive, old_text, new_text, match_kind) {
  const end_line = if end_line_exclusive > start_line {
    end_line_exclusive - 1
  } else {
    start_line
  }
  return {
    start_line: start_line,
    end_line: end_line,
    end_line_exclusive: end_line_exclusive,
    old_line_count: max(end_line_exclusive - start_line, 0),
    new_line_count: len(split(new_text ?? "", "\n")),
    old_sha256: edit_patch_content_hash(old_text),
    new_sha256: edit_patch_content_hash(new_text),
    match_kind: match_kind,
  }
}

fn __edit_context(prefix, needle, suffix) {
  const before_lines = split(prefix, "\n")
  const after_lines = split(suffix, "\n")
  const before = if len(before_lines) > 2 {
    join(before_lines[-2:], "\n")
  } else {
    prefix
  }
  const after = if len(after_lines) > 2 {
    join(after_lines[:2], "\n")
  } else {
    suffix
  }
  return trim(before + needle + after)
}

fn __edit_candidate_contexts(parts, old_text, max_contexts) {
  let contexts = []
  let prefix = ""
  let idx = 0
  const limit = max_contexts ?? 3
  const needle_lines = max(len(split(old_text ?? "", "\n")), 1)
  while idx < len(parts) - 1 && len(contexts) < limit {
    prefix = prefix + parts[idx]
    const start_line = __edit_start_line(prefix)
    contexts = contexts
      + [
      {
        start_line: start_line,
        end_line: start_line + needle_lines - 1,
        snippet: __edit_context(prefix, old_text, parts[idx + 1]),
      },
    ]
    prefix = prefix + old_text
    idx = idx + 1
  }
  return contexts
}

fn __edit_line_candidate_contexts(text, candidates, max_contexts) {
  const lines = split(text ?? "", "\n")
  let contexts = []
  const limit = max_contexts ?? 3
  let idx = 0
  while idx < len(candidates) && len(contexts) < limit {
    const candidate = candidates[idx]
    const start_line = candidate.start_line
    const end_line_exclusive = candidate.end_line_exclusive
    const prefix_start = max(start_line - 2, 0)
    const suffix_end = min(end_line_exclusive + 2, len(lines))
    const snippet = trim(join(lines[prefix_start:suffix_end], "\n"))
    contexts = contexts
      + [{start_line: start_line, end_line: end_line_exclusive - 1, snippet: snippet}]
    idx = idx + 1
  }
  return contexts
}

fn __edit_error(code, message, text, old_text, new_text, fields = nil) {
  const base = {
    ok: false,
    changed: false,
    error_code: code,
    message: message,
    patched: text,
    before_sha256: edit_patch_content_hash(text),
    after_sha256: edit_patch_content_hash(text),
    old_sha256: edit_patch_content_hash(old_text),
    new_sha256: edit_patch_content_hash(new_text),
    errors: [{code: code, message: message}],
    warnings: [],
    changed_regions: [],
    provenance: {module: "std/edit"},
  }
  return base.merge(fields ?? {})
}

fn __edit_lazy_placeholder_patterns() {
  return [
    "(?im)^\\s*//\\s*\\.\\.\\.?\\s*(rest|remaining|existing|implementation|code|omit)",
    "(?im)^\\s*//\\s*TODO:?\\s*(implement|fill|add|complete)",
    "(?im)^\\s*#\\s*\\.\\.\\.?\\s*(rest|remaining|existing|implementation|code)",
    "(?im)^\\s*/\\*\\s*\\.\\.\\.?\\s*\\*/\\s*$",
    "(?im)^\\s*//\\s*\\.\\.\\.\\s*$",
    "(?im)^\\s*#\\s*\\.\\.\\.\\s*$",
    "(?im)^\\s*pass\\s*#\\s*\\.\\.\\.",
  ]
}

fn __edit_lazy_placeholder_phrases() {
  return ["unchanged", "omitted for brevity", "same as before", "rest of the file", "remaining code"]
}

fn __edit_lazy_match_count(text) {
  const body = text ?? ""
  if body == "" {
    return 0
  }
  let total = 0
  for line in split(body, "\n") {
    const t = lowercase(trim(line))
    if t == "..." || t == "…" {
      total = total + 1
    }
  }
  for pattern in __edit_lazy_placeholder_patterns() {
    const matches = regex_match(pattern, body) ?? []
    total = total + len(matches)
  }
  const lowered = lowercase(body)
  for phrase in __edit_lazy_placeholder_phrases() {
    if contains(lowered, phrase) {
      total = total + 1
    }
  }
  return total
}

fn __edit_has_lazy_placeholder(new_text) {
  return __edit_lazy_match_count(new_text) > 0
}

fn __edit_guardrails(old_text, new_text, options) {
  const opts = options ?? {}
  if old_text == "" && !(opts?.allow_empty_old_text ?? false) {
    return {code: "empty_old_text", message: "old_text must not be empty"}
  }
  if old_text == new_text && !(opts?.allow_noop ?? false) {
    return {code: "no_op", message: "patch does not change the selected text"}
  }
  if __edit_collapse_ws(old_text) == __edit_collapse_ws(new_text)
    && old_text != new_text
    && !(opts?.allow_whitespace_only ?? false) {
    return {code: "whitespace_only", message: "patch changes only whitespace"}
  }
  if __edit_has_lazy_placeholder(new_text) && !(opts?.allow_lazy_placeholders ?? false) {
    return {code: "lazy_placeholder", message: "patch contains an omission or unchanged-content placeholder"}
  }
  const old_len = len(old_text)
  const new_len = len(new_text)
  const growth = new_len - old_len
  const max_growth_bytes = opts?.max_growth_bytes ?? 20000
  if max_growth_bytes != nil && growth > max_growth_bytes {
    return {code: "excessive_growth", message: "patch grows selected text by more than max_growth_bytes"}
  }
  const max_growth_ratio = opts?.max_growth_ratio ?? 8
  if max_growth_ratio != nil && growth > 1024 && new_len > old_len * max_growth_ratio {
    return {code: "excessive_growth", message: "patch grows selected text by more than max_growth_ratio"}
  }
  return nil
}

fn __edit_success(
  text,
  patched,
  old_text,
  new_text,
  match_kind,
  start_line,
  end_line_exclusive,
  options,
) {
  const before_hash = edit_patch_content_hash(text)
  const after_hash = edit_patch_content_hash(patched)
  const expected_region = __edit_region(start_line, end_line_exclusive, old_text, new_text, match_kind)
  return {
    ok: true,
    changed: text != patched,
    patched: patched,
    match_kind: match_kind,
    start_line: expected_region.start_line,
    end_line: expected_region.end_line,
    end_line_exclusive: expected_region.end_line_exclusive,
    expected_region: expected_region,
    changed_regions: edit_changed_regions(text, patched),
    before_sha256: before_hash,
    after_sha256: after_hash,
    old_sha256: edit_patch_content_hash(old_text),
    new_sha256: edit_patch_content_hash(new_text),
    errors: [],
    warnings: [],
    provenance: {
      module: "std/edit",
      helper: "edit_apply_old_new_patch",
      match_kind: match_kind,
      before_sha256: before_hash,
      after_sha256: after_hash,
      caller: options?.provenance,
    },
  }
}

fn __edit_splice_raw(text, start_line, end_line_exclusive, new_text) {
  const lines = split(text ?? "", "\n")
  let out = []
  if start_line > 0 {
    out = out + lines[:start_line]
  }
  if (new_text ?? "") != "" {
    out = out + split(new_text ?? "", "\n")
  }
  if end_line_exclusive < len(lines) {
    out = out + lines[end_line_exclusive:]
  }
  return join(out, "\n")
}

fn __edit_has_distinctive_token(line, min_chars) {
  const chars = min_chars ?? 4
  if chars <= 0 {
    return true
  }
  const tokens = regex_match("[A-Za-z0-9_]+", line ?? "") ?? []
  for token in tokens {
    if len(token) >= chars {
      return true
    }
  }
  return false
}

fn __edit_structural_anchors_ok(old_text, options) {
  const opts = options ?? {}
  const min_lines = opts?.structural_min_nonblank_lines ?? 3
  const anchor_chars = opts?.structural_anchor_chars ?? 4
  const anchor_mode = lowercase(opts?.structural_require_anchored_lines ?? "both")
  const needle_lines = split(old_text ?? "", "\n")
  let nonblank_lines = []
  for line in needle_lines {
    if __edit_structural_line(line) != "" {
      nonblank_lines = nonblank_lines + [line]
    }
  }
  if len(nonblank_lines) < min_lines {
    return false
  }
  if anchor_mode == "none" || anchor_chars <= 0 {
    return true
  }
  const first = nonblank_lines[0] ?? ""
  const last = nonblank_lines[len(nonblank_lines) - 1] ?? ""
  const first_ok = __edit_has_distinctive_token(first, anchor_chars)
  const last_ok = __edit_has_distinctive_token(last, anchor_chars)
  if anchor_mode == "either" {
    return first_ok || last_ok
  }
  return first_ok && last_ok
}

fn __edit_line_candidates(text, old_text, structural, options) {
  const lines = split(text ?? "", "\n")
  let candidates = []
  const target = __edit_signature(old_text, structural)
  if target == "" {
    return candidates
  }
  if !structural {
    const width = len(split(old_text ?? "", "\n"))
    let start = 0
    while start + width <= len(lines) {
      const segment = join(lines[start:start + width], "\n")
      if __edit_signature(segment, false) == target {
        candidates = candidates + [{start_line: start, end_line_exclusive: start + width, text: segment}]
      }
      start = start + 1
    }
    return candidates
  }
  if !__edit_structural_anchors_ok(old_text, options) {
    return candidates
  }
  const target_count = __edit_nonblank_count(split(old_text ?? "", "\n"))
  let start = 0
  while start < len(lines) {
    if __edit_structural_line(lines[start]) == "" {
      start = start + 1
      continue
    }
    let end = start
    let nonblank = 0
    while end < len(lines) && nonblank < target_count {
      if __edit_structural_line(lines[end]) != "" {
        nonblank = nonblank + 1
      }
      end = end + 1
    }
    if nonblank == target_count {
      while end < len(lines) && __edit_structural_line(lines[end]) == "" {
        end = end + 1
      }
      const segment = join(lines[start:end], "\n")
      if __edit_signature(segment, true) == target {
        candidates = candidates + [{start_line: start, end_line_exclusive: end, text: segment}]
      }
    }
    start = start + 1
  }
  return candidates
}

fn __edit_apply_line_candidate(text, old_text, new_text, match_kind, candidates, options) {
  if len(candidates) == 0 {
    return nil
  }
  const opts = options ?? {}
  if len(candidates) > 1 {
    return __edit_error(
      "ambiguous_match",
      "old_text matched multiple normalized regions",
      text,
      old_text,
      new_text,
      {
        candidate_count: len(candidates),
        match_kind: match_kind,
        candidate_contexts: __edit_line_candidate_contexts(text, candidates, opts?.max_candidate_contexts),
      },
    )
  }
  const candidate = candidates[0]
  const patched = __edit_splice_raw(text, candidate.start_line, candidate.end_line_exclusive, new_text)
  const result = __edit_success(
    text,
    patched,
    candidate.text,
    new_text,
    match_kind,
    candidate.start_line,
    candidate.end_line_exclusive,
    opts,
  )
  if match_kind == "structural" || match_kind == "line" {
    return result.merge({whitespace_explanation: edit_explain_whitespace_difference(old_text, candidate.text)})
  }
  return result
}

/**
 * Apply one old/new anchored patch to text.
 *
 * Returns `{ok, changed, patched, match_kind, start_line, end_line,
 * before_sha256, after_sha256, changed_regions, errors, warnings, provenance}`.
 * Matching is exact first by default, then whitespace-normalized line matching,
 * then structural matching that ignores blank lines and whitespace.
 *
 * Structural matches are conservative by default: the needle must contain at
 * least `structural_min_nonblank_lines` (3) non-blank lines, and both the
 * first and last non-blank anchor lines must carry a distinctive token of at
 * least `structural_anchor_chars` (4) alphanumeric characters. Relax with
 * `structural_require_anchored_lines: "either"` or `"none"` only when callers
 * have a host-side validator that can re-check the result. Pass
 * `strip_line_numbers: true` to pre-strip `   N | ` line-number prefixes from
 * `old_text` when the model pasted them straight from a numbered file read.
 *
 * @effects: []
 * @errors: []
 */
pub fn edit_apply_old_new_patch(text, old_text, new_text, options = nil) {
  const source = text ?? ""
  const raw_old = old_text ?? ""
  const new = new_text ?? ""
  const opts = options ?? {}
  const old = if opts?.strip_line_numbers ?? false {
    edit_strip_line_number_prefixes(raw_old)
  } else {
    raw_old
  }
  const guardrail = __edit_guardrails(old, new, opts)
  if guardrail != nil {
    return __edit_error(guardrail.code, guardrail.message, source, old, new)
  }
  const mode = opts?.match ?? "auto"
  if mode != "line" && mode != "structural" {
    const parts = split(source, old)
    if len(parts) == 2 {
      const start_line = __edit_start_line(parts[0])
      const end_line_exclusive = start_line + len(split(old, "\n"))
      return __edit_success(
        source,
        parts[0] + new + parts[1],
        old,
        new,
        "exact",
        start_line,
        end_line_exclusive,
        opts,
      )
    }
    if len(parts) > 2 {
      return __edit_error(
        "ambiguous_match",
        "old_text matched multiple exact regions",
        source,
        old,
        new,
        {
          candidate_count: len(parts) - 1,
          candidate_contexts: __edit_candidate_contexts(parts, old, opts?.max_candidate_contexts ?? 3),
        },
      )
    }
    if mode == "exact" {
      return __edit_error("no_match", "old_text did not match exactly", source, old, new)
    }
  }
  if mode == "line" || mode == "auto" {
    const line_result = __edit_apply_line_candidate(
      source,
      old,
      new,
      "line",
      __edit_line_candidates(source, old, false, opts),
      opts,
    )
    if line_result != nil {
      return line_result
    }
    if mode == "line" {
      return __edit_error("no_match", "old_text did not match any normalized line region", source, old, new)
    }
  }
  if mode == "structural" || mode == "auto" {
    const structural_result = __edit_apply_line_candidate(
      source,
      old,
      new,
      "structural",
      __edit_line_candidates(source, old, true, opts),
      opts,
    )
    if structural_result != nil {
      return structural_result
    }
  }
  return __edit_error("no_match", "old_text did not match any safe patch region", source, old, new)
}

/**
 * Splice a half-open 0-based line range and return patch metadata.
 *
 * @effects: []
 * @errors: []
 */
pub fn edit_splice_lines(text, start_line, end_line_exclusive, new_text, options = nil) {
  const source = text ?? ""
  const lines = split(source, "\n")
  const start = start_line ?? 0
  const end = end_line_exclusive ?? start
  if start < 0 || end < start || end > len(lines) {
    return __edit_error(
      "invalid_line_range",
      "line range must be 0-based, half-open, and inside the text",
      source,
      "",
      new_text ?? "",
    )
  }
  const old = join(lines[start:end], "\n")
  const guardrail = __edit_guardrails(old, new_text ?? "", (options ?? {}).merge({allow_empty_old_text: true}))
  if guardrail != nil {
    return __edit_error(guardrail.code, guardrail.message, source, old, new_text ?? "")
  }
  const patched = __edit_splice_raw(source, start, end, new_text ?? "")
  return __edit_success(source, patched, old, new_text ?? "", "line_splice", start, end, options ?? {})
}

fn __edit_find_resync(before_lines, after_lines, before_index, after_index) {
  const window = 80
  let distance = 1
  while distance <= window {
    let before_delta = 0
    while before_delta <= distance {
      const after_delta = distance - before_delta
      const next_before = before_index + before_delta
      const next_after = after_index + after_delta
      if next_before < len(before_lines)
        && next_after < len(after_lines)
        && before_lines[next_before] == after_lines[next_after] {
        return {before_index: next_before, after_index: next_after}
      }
      before_delta = before_delta + 1
    }
    distance = distance + 1
  }
  return {before_index: len(before_lines), after_index: len(after_lines)}
}

fn __edit_hunk(before_start, after_start, before_end, after_end, next_before, next_after) {
  return {
    start_line: min(before_start, after_start),
    end_line: max(before_end, after_end),
    end_line_exclusive: max(next_before, next_after),
    before_start_line: before_start,
    after_start_line: after_start,
    before_end_line: before_end,
    after_end_line: after_end,
    before_line_count: max(before_end - before_start + 1, 0),
    after_line_count: max(after_end - after_start + 1, 0),
  }
}

/**
 * Return deterministic line-level changed-region metadata.
 *
 * @effects: []
 * @errors: []
 */
pub fn edit_changed_regions(before, after) {
  const before_lines = split(before ?? "", "\n")
  const after_lines = split(after ?? "", "\n")
  let regions = []
  let before_index = 0
  let after_index = 0
  while before_index < len(before_lines) || after_index < len(after_lines) {
    if before_index < len(before_lines)
      && after_index < len(after_lines)
      && before_lines[before_index] == after_lines[after_index] {
      before_index = before_index + 1
      after_index = after_index + 1
      continue
    }
    const before_start = before_index
    const after_start = after_index
    const resync = __edit_find_resync(before_lines, after_lines, before_index, after_index)
    const next_before = resync.before_index
    const next_after = resync.after_index
    regions = regions
      + [__edit_hunk(before_start, after_start, next_before - 1, next_after - 1, next_before, next_after)]
    before_index = next_before
    after_index = next_after
  }
  return regions
}

fn __edit_expected_end(region) {
  if region?.end_line != nil {
    return region.end_line
  }
  if region?.end_line_exclusive != nil {
    return region.end_line_exclusive - 1
  }
  return region?.start_line ?? 0
}

fn __edit_region_within(actual, expected) {
  const expected_start = expected?.start_line ?? 0
  const expected_end = __edit_expected_end(expected)
  return actual.start_line >= expected_start && actual.end_line <= expected_end
}

/**
 * Strip `   N | ` line-number prefixes from raw text when at least 60% of
 * non-empty lines carry that shape. Useful preprocessing for old_text strings
 * that a model pasted verbatim from a numbered file read; otherwise the text
 * never matches because each anchor line has an extra `42 | ` prefix.
 *
 * The 60% threshold is intentional: a file that legitimately contains one or
 * two `N | …` lines (e.g. a docstring example) is left alone.
 *
 * @effects: []
 * @errors: []
 */
pub fn edit_strip_line_number_prefixes(text) {
  const raw = text ?? ""
  if raw == "" {
    return raw
  }
  const lines = split(raw, "\n")
  let non_empty_total = 0
  let matching = 0
  for line in lines {
    if trim(line) == "" {
      continue
    }
    non_empty_total = non_empty_total + 1
    if regex_match("^\\s*\\d+\\s*\\| ", line) {
      matching = matching + 1
    }
  }
  if non_empty_total == 0 {
    return raw
  }
  if matching * 100 / non_empty_total <= 60 {
    return raw
  }
  let stripped = []
  for line in lines {
    stripped = stripped + [regex_replace("^\\s*\\d+\\s*\\| ", "", line)]
  }
  return join(stripped, "\n")
}

fn __edit_count_tab_indent(lines) {
  let total = 0
  for line in lines {
    if (line ?? "").starts_with("\t") {
      total = total + 1
    }
  }
  return total
}

fn __edit_count_space_indent(lines) {
  let total = 0
  for line in lines {
    const raw = line ?? ""
    if raw == "" || raw.starts_with("\t") {
      continue
    }
    if raw.starts_with(" ") {
      total = total + 1
    }
  }
  return total
}

fn __edit_min_indent(lines) {
  let smallest = -1
  for line in lines {
    const raw = line ?? ""
    if trim(raw) == "" {
      continue
    }
    const leading = len(raw) - len(regex_replace("^[ \\t]+", "", raw))
    if smallest == -1 || leading < smallest {
      smallest = leading
    }
  }
  return smallest
}

fn __edit_count_blank_lines(lines) {
  let total = 0
  for line in lines {
    if trim(line ?? "") == "" {
      total = total + 1
    }
  }
  return total
}

/**
 * Diagnose the dominant whitespace discrepancy between an old_text needle and
 * the actual matched span in the source. Hosts log this on fuzzy/structural
 * matches so the model can learn from each near-miss.
 *
 * Returns a short human-readable sentence such as
 * `"your old_string used tabs but the file uses spaces"` or
 * `"your old_string had 1 extra blank line(s) that the file does not"`.
 * Returns `""` when needle and matched are identical or no dominant cause is
 * detectable.
 *
 * @effects: []
 * @errors: []
 */
pub fn edit_explain_whitespace_difference(needle, matched) {
  const needle_text = needle ?? ""
  const matched_text = matched ?? ""
  if needle_text == matched_text {
    return ""
  }
  const needle_lines = split(needle_text, "\n")
  const matched_lines = split(matched_text, "\n")
  const needle_tabs = __edit_count_tab_indent(needle_lines)
  const needle_spaces = __edit_count_space_indent(needle_lines)
  const matched_tabs = __edit_count_tab_indent(matched_lines)
  const matched_spaces = __edit_count_space_indent(matched_lines)
  if needle_tabs > 0 && matched_tabs == 0 && matched_spaces > 0 {
    return "your old_string used tabs but the file uses spaces"
  }
  if needle_spaces > 0 && matched_spaces == 0 && matched_tabs > 0 {
    return "your old_string used spaces but the file uses tabs"
  }
  const needle_min = __edit_min_indent(needle_lines)
  const matched_min = __edit_min_indent(matched_lines)
  if needle_min != matched_min && needle_min >= 0 && matched_min >= 0 {
    return "your old_string's base indent was ${needle_min} but the file's matched block starts at indent ${matched_min}"
  }
  const needle_blanks = __edit_count_blank_lines(needle_lines)
  const matched_blanks = __edit_count_blank_lines(matched_lines)
  if needle_blanks != matched_blanks {
    const delta = matched_blanks - needle_blanks
    if delta > 0 {
      return "your old_string was missing ${delta} blank line(s) that the file has"
    }
    return "your old_string had ${0 - delta} extra blank line(s) that the file does not"
  }
  return "minor whitespace formatting (exact cause not pinpointed)"
}

/**
 * Detect whether a whole-file edit looks like a lazy truncation: a file with
 * at least `min_old_lines` (10) lines shrunk below `min_keep_pct` (35%) of
 * its original line count *and* the new content still contains at least one
 * lazy placeholder.
 *
 * Returns `{ok, lazy, error_code, message, old_lines, new_lines, lazy_hits,
 * provenance}`. `ok` is true when the edit is sound; false when the
 * shrinkage + placeholder shape is present. Distinct from
 * `edit_apply_old_new_patch`'s `lazy_placeholder` guardrail, which fires on
 * any placeholder in the patch region — this one is for whole-file rewrites
 * where placeholders by themselves are not a signal.
 *
 * @effects: []
 * @errors: []
 */
pub fn edit_check_lazy_truncation(old_content, new_content, options = nil) {
  const opts = options ?? {}
  const {min_old_lines = 10, min_keep_pct = 35} = opts ?? {}
  const old_text = old_content ?? ""
  const new_text = new_content ?? ""
  const old_lines = len(split(old_text, "\n"))
  const new_lines = len(split(new_text, "\n"))
  const lazy_hits = __edit_lazy_match_count(new_text)
  const provenance = {
    module: "std/edit",
    helper: "edit_check_lazy_truncation",
    before_sha256: edit_patch_content_hash(old_text),
    after_sha256: edit_patch_content_hash(new_text),
    caller: opts?.provenance,
  }
  const neutral = {
    ok: true,
    lazy: false,
    error_code: nil,
    message: "",
    old_lines: old_lines,
    new_lines: new_lines,
    lazy_hits: lazy_hits,
    provenance: provenance,
  }
  if old_lines < min_old_lines {
    return neutral
  }
  const threshold = old_lines * min_keep_pct / 100
  if new_lines > threshold {
    return neutral
  }
  if lazy_hits == 0 {
    return neutral
  }
  return {
    ok: false,
    lazy: true,
    error_code: "lazy_truncation",
    message: "lazy edit: file was truncated from ${old_lines} to ${new_lines} lines with placeholder comments — provide the complete implementation",
    old_lines: old_lines,
    new_lines: new_lines,
    lazy_hits: lazy_hits,
    provenance: provenance,
  }
}

/**
 * Validate that before/after text differs only inside expected line regions.
 * Expected regions use inclusive `end_line` or half-open `end_line_exclusive`.
 *
 * @effects: []
 * @errors: []
 */
pub fn edit_validate_changed_regions(before, after, expected_regions, options = nil) {
  const actual = edit_changed_regions(before ?? "", after ?? "")
  const expected = expected_regions ?? []
  let errors = []
  for region in actual {
    let matched = false
    for expected_region in expected {
      if __edit_region_within(region, expected_region) {
        matched = true
        break
      }
    }
    if !matched {
      errors = errors
        + [
        {
          code: "unexpected_changed_region",
          message: "changed region falls outside expected patch range",
          region: region,
        },
      ]
    }
  }
  return {
    ok: len(errors) == 0,
    actual_regions: actual,
    expected_regions: expected,
    errors: errors,
    error_codes: errors.map({ error -> error.code }),
    warnings: [],
    provenance: {
      module: "std/edit",
      helper: "edit_validate_changed_regions",
      before_sha256: edit_patch_content_hash(before ?? ""),
      after_sha256: edit_patch_content_hash(after ?? ""),
      caller: options?.provenance,
    },
  }
}

/**
 * Locate one or more AST nodes via a Tree-Sitter query and replace each
 * match's bytes with `replacement`. The byte splice preserves leading
 * indentation, trailing trivia, and any whitespace outside the matched
 * span — so this is the precise alternative to freeform text patching
 * for "change this function body" / "rename this call" style edits.
 *
 * The query must declare at least one capture; the capture named by
 * `target_capture` (default `"target"`) is the replaceable span.
 * Single-capture queries accept any capture name.
 *
 * Multi-match policy via `select`:
 *
 * - `"unique"` (default) requires exactly one match; else `ambiguous`.
 * - `"first"` picks the lowest byte offset.
 * - `"all"` rewrites every match.
 * - `"nth"` plus `nth: N` picks the 1-based index in document order.
 *
 * When `validate` is true (default) the rewritten source is re-parsed and
 * any tree-sitter ERROR/MISSING node aborts the edit with
 * `result == "syntax_error"`. When `dry_run` is true the file is left
 * untouched but the response still carries the `preview` text the splice
 * would produce.
 *
 * Reads and writes route through staged-fs (#1722) when a `session_id` is
 * supplied so the edit is atomic alongside siblings.
 *
 * @effects: [host, fs]
 * @errors: [backend]
 * @api_stability: experimental
 * @example: edit_apply_node({path: "src/lib.rs", query: query, replacement: "{ 42 }"})
 */
pub fn edit_apply_node(params) {
  const raw = hostlib_ast_apply_node(params ?? {})
  const payload = raw ?? {}
  const provenance = {
    module: "std/edit",
    helper: "edit_apply_node",
    path: payload?.path,
    dry_run: payload?.dry_run ?? false,
    before_sha256: payload?.before_sha256,
    after_sha256: payload?.after_sha256,
    caller: params?.provenance,
  }
  return {
    ok: (payload?.result ?? "") == "applied",
    applied: payload?.applied ?? false,
    result: payload?.result ?? "no_match",
    path: payload?.path,
    dry_run: payload?.dry_run ?? false,
    match_count: payload?.match_count ?? 0,
    edits: payload?.edits ?? [],
    spans: payload?.spans ?? [],
    preview: payload?.preview,
    before_sha256: payload?.before_sha256,
    after_sha256: payload?.after_sha256,
    query: payload?.query,
    target_capture: payload?.target_capture,
    details: payload?.details,
    fallback_suggestion: payload?.fallback_suggestion,
    error_row: payload?.error_row,
    error_column: payload?.error_column,
    errors: [],
    warnings: [],
    provenance: provenance,
  }
}

/**
 * Splice `content` into `path` relative to a unique AST anchor located
 * by a Tree-Sitter query.
 *
 * Companion to `edit_apply_node`: where `apply_node` *replaces* a span,
 * this primitive *adds* a sibling or child node. `position` picks the
 * slot:
 *
 * - `"before"` / `"after"` — insert a sibling at the anchor's indent
 *   depth (e.g. "add a new function after this one").
 * - `"first_child"` / `"last_child"` — insert inside the anchor at the
 *   inferred child depth (e.g. "append a new test to this mod").
 *
 * The query MUST match exactly one node — multi-match returns
 * `result == "ambiguous"`. Tighten queries with `(#eq? @name "…")`
 * predicates to disambiguate.
 *
 * Each line of `content` is re-indented to the target depth unless
 * `reindent: false` is supplied. The indent unit is detected from the
 * file's existing indentation (tabs win when any line starts with one,
 * else the smallest non-zero leading-space run), falling back to a
 * language default. Override explicitly via `indent: "  "`.
 *
 * When `validate` is true (default) the rewritten source is re-parsed
 * and any tree-sitter ERROR/MISSING node aborts the edit with
 * `result == "syntax_error"`. When `dry_run` is true the file is left
 * untouched but the response still carries the `preview` text the
 * splice would produce. Reads and writes route through staged-fs
 * (#1722) when a `session_id` is supplied so the insert is atomic
 * alongside siblings.
 *
 * @effects: [host, fs]
 * @errors: [backend]
 * @api_stability: experimental
 * @example: edit_insert_at_anchor({path: "src/lib.rs", query: q, position: "after", content: "fn beta() {}"})
 */
pub fn edit_insert_at_anchor(params) {
  const raw = hostlib_ast_insert_at_anchor(params ?? {})
  const payload = raw ?? {}
  const provenance = {
    module: "std/edit",
    helper: "edit_insert_at_anchor",
    path: payload?.path,
    position: payload?.position,
    dry_run: payload?.dry_run ?? false,
    before_sha256: payload?.before_sha256,
    after_sha256: payload?.after_sha256,
    caller: params?.provenance,
  }
  return {
    ok: (payload?.result ?? "") == "applied",
    applied: payload?.applied ?? false,
    result: payload?.result ?? "no_match",
    path: payload?.path,
    dry_run: payload?.dry_run ?? false,
    position: payload?.position,
    insertion_byte: payload?.insertion_byte,
    indent: payload?.indent,
    inserted_text: payload?.inserted_text,
    anchor: payload?.anchor,
    anchors: payload?.anchors ?? [],
    match_count: payload?.match_count ?? 0,
    preview: payload?.preview,
    before_sha256: payload?.before_sha256,
    after_sha256: payload?.after_sha256,
    query: payload?.query,
    target_capture: payload?.target_capture,
    details: payload?.details,
    fallback_suggestion: payload?.fallback_suggestion,
    error_row: payload?.error_row,
    error_column: payload?.error_column,
    errors: [],
    warnings: [],
    provenance: provenance,
  }
}

/**
 * Run one Tree-Sitter `query` -> `replacement` codemod over every file in
 * `paths`, returning a per-file preview plus a roll-up `summary`.
 *
 * This is the multi-file sibling of `edit_apply_node`: each file goes
 * through the same format-preserving byte-splice, so indentation and
 * trivia outside each matched span survive untouched.
 *
 * `params` is a dict:
 *
 * - `paths`: non-empty list of files. Duplicates are collapsed.
 * - `query`: Tree-Sitter S-expression with at least one capture; the
 *   `target_capture` (default `"target"`) capture is the replaceable span.
 * - `replacement` (alias `fix`): text spliced in for each selected node.
 * - `select`: per-file multi-match policy (`"unique"` default, or
 *   `"first" | "all" | "nth"` with `nth`).
 * - `language`: optional grammar hint applied to every path.
 * - `validate`: re-parse each edit and reject ERROR/MISSING nodes (default).
 *
 * **Dry-run is the default.** A plain call previews edits across every file
 * without touching disk; pass `dry_run: false` to apply. A failure on one
 * file (no match, a query invalid for that grammar, a post-edit syntax
 * error, an unreadable path) is recorded as that file's `result` and does
 * not abort the batch. Re-running an applied codemod reports zero further
 * changes (`files_changed: 0`), which is the A6 idempotency hook.
 *
 * `ok` is true when no file failed. Each `files` entry carries `path`,
 * `result`, `match_count`, `changed`, `before_sha256`, `after_sha256`, and
 * `preview`; `summary` rolls up `files_total / files_matched /
 * files_changed / files_written / files_failed / match_count_total`.
 *
 * @effects: [host, fs]
 * @errors: [backend]
 * @api_stability: experimental
 * @example: edit_batch_apply({paths: ["a.rs", "b.rs"], query: q, replacement: "{ 0 }"})
 */
pub fn edit_batch_apply(params) {
  const payload = hostlib_ast_batch_apply(params ?? {}) ?? {}
  return payload
    .merge(
    {
      ok: (payload?.summary?.files_failed ?? 1) == 0,
      provenance: {module: "std/edit", helper: "edit_batch_apply", caller: params?.provenance},
    },
  )
}