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-- Apply a batch of exact-text replacements to a file. Keep the tool
-- description terse; the rules are enforced here rather than re-stated
-- in prose, with the rejection message naming exactly which rule each
-- entry tripped so the model can self-correct on the next call.
--
-- Rejection rules (atomic — any failure rejects the whole call):
-- 1. Each `old` must occur exactly once in the original file.
-- 2. `old` may not be the empty string.
-- 3. Resolved ranges of `old` matches must not overlap.
-- All matches are evaluated against the original file, not
-- progressively against the result of earlier entries.
return {
name = "std.edit",
description = "Apply exact-text replacements to a file. Each entry's `old` must match exactly once in the original file (not progressively). Edits whose ranges overlap, match zero times, or match multiple times reject the entire call — no partial edits, file untouched. Keep `old` minimal but unique; widen with surrounding context if needed.",
schema = {
type = "object",
properties = {
path = { type = "string", description = "Path to the file (relative or absolute)." },
edits = {
type = "array",
description = "Replacements applied atomically.",
minItems = 1,
items = {
type = "object",
properties = {
old = { type = "string", description = "Exact substring to find; must appear exactly once." },
new = { type = "string", description = "Replacement text (may be empty to delete)." },
},
required = { "old", "new" },
},
},
},
required = { "path", "edits" },
},
handler = function(input)
local path = input.path
local edits = input.edits
if type(path) ~= "string" or path == "" then
return "Error: `path` must be a non-empty string."
end
if type(edits) ~= "table" or #edits == 0 then
return "Error: `edits` must be a non-empty array."
end
-- Load the file.
local f, open_err = io.open(path, "rb")
if not f then
return "Error: " .. (open_err or ("could not open " .. path))
end
local original = f:read("a")
f:close()
if not original then
return "Error: failed to read " .. path
end
-- Validate every entry first, collecting the byte-range each
-- `before` resolves to. We need this in two passes:
-- 1. uniqueness check (count occurrences)
-- 2. overlap check (compare resolved ranges pairwise)
local problems = {} -- list of "edit #N: ..." strings
local ranges = {} -- per-edit { start_byte, end_byte } or nil
for i, e in ipairs(edits) do
if type(e) ~= "table" then
problems[#problems + 1] = string.format(
"edit #%d: entry is not an object", i
)
ranges[i] = nil
elseif type(e.old) ~= "string" or type(e.new) ~= "string" then
problems[#problems + 1] = string.format(
"edit #%d: `old` and `new` must both be strings", i
)
ranges[i] = nil
elseif e.old == "" then
problems[#problems + 1] = string.format(
"edit #%d: `old` is the empty string (would be ambiguous)", i
)
ranges[i] = nil
else
-- string.find with `plain = true` skips pattern parsing,
-- so the search is literal. Count occurrences by walking.
local count = 0
local first_start, first_end = nil, nil
local search_from = 1
while true do
local s, ee = string.find(original, e.old, search_from, true)
if not s then break end
count = count + 1
if count == 1 then
first_start, first_end = s, ee
end
search_from = ee + 1
end
if count == 0 then
-- Truncate the previewed snippet so the error stays
-- legible in tool output.
local snippet = e.old
if #snippet > 80 then
snippet = snippet:sub(1, 77) .. "..."
end
problems[#problems + 1] = string.format(
"edit #%d: `old` not found in file. Snippet: %q",
i, snippet
)
ranges[i] = nil
elseif count > 1 then
problems[#problems + 1] = string.format(
"edit #%d: `old` matches %d times (need exactly 1). " ..
"Widen with surrounding context to disambiguate.",
i, count
)
ranges[i] = nil
else
ranges[i] = { first_start, first_end }
end
end
end
-- Overlap check (only meaningful if we got this far without
-- per-edit problems; otherwise the user already has plenty to
-- fix and overlap noise would be confusing).
if #problems == 0 then
for i = 1, #ranges do
for j = i + 1, #ranges do
local a, b = ranges[i], ranges[j]
if a and b and not (a[2] < b[1] or b[2] < a[1]) then
problems[#problems + 1] = string.format(
"edits #%d and #%d target overlapping regions " ..
"(bytes %d-%d and %d-%d). Combine them into one " ..
"edit with a wider `old`.",
i, j, a[1], a[2], b[1], b[2]
)
end
end
end
end
if #problems > 0 then
return "Error: edit rejected (" .. #problems .. " issue" ..
(#problems == 1 and "" or "s") .. "); file not modified.\n" ..
" - " .. table.concat(problems, "\n - ") .. "\n"
end
-- Apply edits. We sort by start position ascending and rebuild
-- the file from non-overlapping slices. This avoids the O(N*M)
-- repeated-substring-substitution and keeps each edit's
-- `before` matched against the original (not the in-progress
-- result).
local order = {}
for i = 1, #edits do order[i] = i end
table.sort(order, function(a, b)
return ranges[a][1] < ranges[b][1]
end)
local out = {}
local cursor = 1
for _, idx in ipairs(order) do
local r = ranges[idx]
if r[1] > cursor then
out[#out + 1] = original:sub(cursor, r[1] - 1)
end
out[#out + 1] = edits[idx].new
cursor = r[2] + 1
end
if cursor <= #original then
out[#out + 1] = original:sub(cursor)
end
local new_content = table.concat(out)
-- Write back.
local wf, werr = io.open(path, "wb")
if not wf then
return "Error: file read OK but failed to reopen for write: " ..
(werr or "?")
end
local ok, write_err = wf:write(new_content)
if not ok then
wf:close()
return "Error: write failed: " .. tostring(write_err)
end
local close_ok, close_err = wf:close()
if not close_ok then
return "Error: close failed: " .. tostring(close_err)
end
return string.format(
"Applied %d edit%s to %s. File is now %d bytes (was %d).",
#edits, (#edits == 1 and "" or "s"), path, #new_content, #original
)
end,
}
|
