# Script Task Templates

When creating a script-mode task, always use one of these templates. The template handles all boilerplate (input parsing, validation, iteration, error handling, summary). You only write the task-specific logic.

## Inputs

All task inputs defined in the TASK.md frontmatter are available to the script in two ways:

1. **Environment variables**: `INPUT_<NAME>` (uppercase) — e.g. `file_path` → `$INPUT_FILE_PATH`
2. **Positional arguments**: if `args: [file_path]` is set in TASK.md, the value is passed as `$1`

## Templates

### 1. File Processor

Use when the task operates on a file or directory of files.

**When to use**: converting files, transcoding, extracting metadata, batch renaming, any per-file operation.

**Structure**: Define `EXTENSIONS` and `process_file()`, then the template handles discovery, iteration, and summary.

```bash
#!/usr/bin/env bash
set -euo pipefail

# ── Task: <Task Name> ──

EXTENSIONS="ext1|ext2|ext3"

process_file() {
  local input="$1"
  # ... do work on $input ...
  # return 0 on success, 1 on failure
}

# ── Template: File Processor ──

TARGET="${1:-${INPUT_FILE_PATH:-}}"

if [[ -z "$TARGET" ]]; then
  echo "Error: No file or directory path provided" >&2
  exit 1
fi

if [[ ! -e "$TARGET" ]]; then
  echo "Error: Path does not exist: $TARGET" >&2
  exit 1
fi

converted=0
failed=0

if [[ -f "$TARGET" ]]; then
  if process_file "$TARGET"; then
    converted=$((converted + 1))
  else
    failed=$((failed + 1))
  fi
elif [[ -d "$TARGET" ]]; then
  while IFS= read -r -d '' file; do
    if process_file "$file"; then
      converted=$((converted + 1))
    else
      failed=$((failed + 1))
    fi
  done < <(find "$TARGET" -type f -regextype posix-extended -iregex ".*\.($EXTENSIONS)" -print0 | sort -z)

  if [[ $converted -eq 0 && $failed -eq 0 ]]; then
    echo "No matching files found in: $TARGET"
    exit 0
  fi
else
  echo "Error: Not a file or directory: $TARGET" >&2
  exit 1
fi

echo ""
echo "Summary: $converted processed, $failed failed"
```

**Slots to fill**:
- `EXTENSIONS` — pipe-separated list of file extensions to match when processing a directory
- `process_file()` — receives one argument: the full path to the file. Print progress to stdout, errors to stderr. Return 0 on success, 1 on failure.

**Example** (convert audio to MP3):
```bash
EXTENSIONS="flac|wav|ogg|wma|aac|m4a|opus"

process_file() {
  local input="$1"
  local output="${input%.*}.mp3"

  if [[ -f "$output" ]]; then
    echo "Skipping (exists): $output"
    return 0
  fi

  echo "Converting: $input"
  if ffmpeg -i "$input" -codec:a libmp3lame -b:a 320k -y "$output" 2>/dev/null; then
    echo "  Done"
  else
    echo "  Failed" >&2
    return 1
  fi
}
```

### 2. Standalone

Use when the task doesn't operate on a specific file target — it uses inputs from environment variables or takes no input at all.

**When to use**: fetching data from APIs, generating reports, system tasks, anything that isn't per-file processing.

```bash
#!/usr/bin/env bash
set -euo pipefail

# ── Task: <Task Name> ──

main() {
  # Access inputs via $INPUT_* environment variables
  # e.g. $INPUT_COUNTRY, $INPUT_LIMIT, $INPUT_OUTPUT_DIR

  # ... do work ...
}

# ── Template: Standalone ──
main
```

**Slots to fill**:
- `main()` — the entire task logic. Use `$INPUT_*` env vars for parameters.

**Example** (download RSS feed):
```bash
main() {
  local url="$INPUT_FEED_URL"
  local output="${INPUT_OUTPUT_DIR:-$HOME}/feed.xml"

  echo "Fetching: $url"
  if curl -sSL "$url" -o "$output"; then
    echo "Saved to: $output"
  else
    echo "Failed to fetch feed" >&2
    exit 1
  fi
}
```

## TASK.md Frontmatter

Every script task needs a TASK.md with this structure:

```yaml
---
name: Task Name
description: What the task does
version: 1
mode: script
language: bash
triggers:                    # optional — enables context menu on matching files
  - type: file
    extensions:
      - ext1
      - ext2
  - type: directory
inputs:
  input_name:
    type: string             # string, number, boolean
    description: What this input is
args: [input_name]           # optional — pass inputs as positional args
---

# Task Name

Brief description of what the task does.
```

## Rules

1. **Always use `set -euo pipefail`** — fail fast on errors.
2. **Print progress to stdout** — the user sees this streamed in the UI.
3. **Print errors to stderr** — they appear in red in the UI.
4. **Return proper exit codes** — 0 = success, non-zero = failure. The UI shows "Task complete" or "Task failed" based on exit code.
5. **Don't assume tools are installed** — check with `command -v` before using optional dependencies.
6. **Use `$INPUT_*` env vars** — never hardcode paths or values that should come from inputs.
7. **The script runs inside a bwrap sandbox** for non-admin users — it has access to `/data/home/` (user's home), `/tmp`, and standard system tools. It cannot access other users' data.
8. **Keep scripts self-contained** — the entire script is stored in the database as a single text blob. No external file dependencies.