#!/usr/bin/env bash
set -uo pipefail

# @describe Apply a patch to a file at the specified path.
# This can be used to edit the file, without having to rewrite the whole file.
# This tool NEVER requests user interaction and NEVER exits with a non-zero code.
# Any error is reported in the tool output so the model can react within the same cycle.
# @option --path! The path of the file to apply to
# @option --contents! The patch to apply to the file
#
# Here is an example of a patch block that can be applied to modify the file to request the user's name:
# --- a/hello.py
# +++ b/hello.py
# \@@ ... @@
#  def hello():
# -    print("Hello World")
# +    name = input("What is your name? ")
# +    print(f"Hello {name}")

# @env LLM_OUTPUT=/dev/stdout The output path

ROOT_DIR="${LLM_ROOT_DIR:-$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)}"
OUT="${LLM_OUTPUT:-/dev/stdout}"

# Report an error in the tool output and finish successfully (exit 0).
err() {
  echo "ERROR: $*" >> "$OUT"
  exit 0
}

main() {
  path="${argc_path:-}"
  patch="${argc_contents:-}"

  [[ -z "$path" ]]  && err "missing --path"
  [[ -z "$patch" ]] && err "missing --contents"
  [[ ! -e "$path" ]] && err "file not found: $path"
  [[ ! -f "$path" ]] && err "not a regular file: $path"
  [[ ! -r "$path" ]] && err "file not readable: $path"

  new_contents=""
  if ! new_contents="$(awk -f "$ROOT_DIR/utils/patch.awk" "$path" <(printf "%s" "$patch") 2>/tmp/fs_patch_new.err)"; then
    msg="$(cat /tmp/fs_patch_new.err 2>/dev/null || true)"
    err "patch apply failed for $path: ${msg:-unknown error}"
  fi

  # Show the diff (if any) so the model sees what is applied.
  # NOTE: no guard_operation.sh here -> no user interaction.
  printf "%s" "$new_contents" | git diff --no-index "$path" - >> "$OUT" 2>/dev/null || true

  if ! printf "%s" "$new_contents" > "$path" 2>/tmp/fs_patch_new_write.err; then
    msg="$(cat /tmp/fs_patch_new_write.err 2>/dev/null || true)"
    err "failed to write patched file $path: ${msg:-unknown error}"
  fi

  echo "The patch applied to: $path" >> "$OUT"
  exit 0
}

# Parse arguments with argc and run the tool in a subshell:
# - argc calls `main`, which always ends with `exit 0`.
# - If argc itself fails (missing/invalid arguments) its generated code prints the
#   error to stderr and calls `exit 1`; running it in a subshell keeps that from
#   terminating this script, and the message is captured into the tool output.
# - The script itself always finishes with exit 0.
argc_err="$(mktemp)"
( eval "$(argc --argc-eval "$0" "$@" 2>/dev/null)" ) 2>"$argc_err"
if [[ -s "$argc_err" ]]; then
  { echo "ERROR: argument parsing failed:"; cat "$argc_err"; } >> "$OUT"
fi
rm -f "$argc_err"
exit 0