# Firefly Import Preprocessor

**Version:** 1.0.0  
**Date:** 03 May 2026  
**Status:** Production Ready

🌐 [Deutsch](README.de.md)

---

## Table of Contents

1. [Overview](#overview)
2. [Installation & Setup](#installation--setup)
3. [Quick Start](#quick-start)
4. [Configuration](#configuration)
5. [Transformation Types](#transformation-types)
6. [CLI Reference](#cli-reference)
7. [Debug Mode](#debug-mode)
8. [Firefly III Integration](#firefly-iii-integration)
9. [Architecture](#architecture)
10. [Error Handling](#error-handling)

---

## Overview

The **Firefly Import Preprocessor** is a production-ready PHP preprocessor for bank CSV export files. It transforms bank data into a standardised format and can optionally import it into Firefly III.

### Core Features

✅ **Full CSV transformation** with complex pipelines  
✅ **Metadata extraction** via regex (IBAN, currency, account name)  
✅ **14 transformation types** for flexible data processing  
✅ **Firefly III integration** — CLI, Docker, and HTTP upload  
✅ **Debug mode** for full processing transparency  
✅ **Production ready** with complete error handling  
✅ **Zero dependencies** for core functionality  

### Workflow

```text
Input CSV
    ↓
Extract metadata (regex)
    ↓
Transform data rows (pipeline)
    ↓
Write output CSV
    ↓
[Optional] Import into Firefly III
```

---

## Installation & Setup

### Requirements

- PHP 8.1+
- Composer (recommended)
- [Optional] Docker for Firefly III integration

### Installation

```bash
# 1. Clone / copy the repository
cd ff-imp-preprocessor

# 2. Install dependencies (optional, dev tools only)
composer install

# 3. Create configuration
cp config/config.example.json config/config.json
# Edit config/config.json with your settings

# 4. Create directories
mkdir -p config/import/{source,output,archive,error}
chmod 755 config/import/{source,output,archive,error}

# 5. Run a test
php bin/transformer.php validate config/config.json input.csv
```

---

## Quick Start

### 1. Adjust configuration

Edit `config/config.json` and make sure the extraction rules match your CSV format:

```json
{
  "metadata": {
    "extractionRules": [
      {
        "name": "account_iban",
        "lineNumber": 2,
        "regex": "IBAN:\\s*([A-Z0-9 ]+)",
        "captureGroup": 1
      }
    ]
  },
  "csvStructure": {
    "headerLine": 5,
    "delimiter": ";",
    "encoding": "UTF-8"
  }
}
```

### 2. Validate CSV

```bash
php bin/transformer.php validate config/config.json input.csv
```

### 3. Run transformation

```bash
php bin/transformer.php transform input.csv config/config.json

# With debug mode for troubleshooting
php bin/transformer.php transform input.csv config/config.json --debug
```

### 4. Inspect output

```bash
php bin/transformer.php test input.csv config/config.json --debug
# Shows up to 10 transformed rows and debug logs
```

---

## Configuration

### config.json structure

#### `metadata` — Metadata extraction

```json
{
  "metadata": {
    "extractionRules": [
      {
        "name": "account_iban",
        "lineNumber": 2,
        "regex": "IBAN:\\s*([A-Z0-9 ]+)",
        "captureGroup": 1
      },
      {
        "name": "currency_code",
        "lineNumber": 3,
        "regex": "Currency:\\s*([A-Z]{3})",
        "captureGroup": 1
      }
    ]
  }
}
```

| Field | Type | Description |
| ------ | ----- | ----------- |
| `name` | string | Name of the metadata variable (used in `constantvalue`) |
| `lineNumber` | int | Line number in CSV (1-based, human-readable) |
| `regex` | string | Regex pattern for extraction (without delimiters) |
| `captureGroup` | int | Capture group index (0 = full match, 1 = first group, etc.) |

**Regex example:**

- Pattern: `IBAN:\s*([A-Z0-9 ]+)`
- Input: `IBAN: CH93 0077 2020 6262 5252 7`
- Capture group 1: `CH93 0077 2020 6262 5252 7`

#### `csvStructure` — CSV format

```json
{
  "csvStructure": {
    "headerLine": 5,
    "delimiter": ";",
    "encoding": "UTF-8",
    "hasBom": false
  }
}
```

| Field | Type | Default | Description |
| ------ | ----- | ------- | ----------- |
| `headerLine` | int | 5 | Line number of the header row (1-based) |
| `delimiter` | string | `;` | CSV delimiter |
| `encoding` | string | `UTF-8` | Character encoding (UTF-8, ISO-8859-1, CP1252) |
| `hasBom` | bool | false | Whether the file has a BOM (Byte Order Mark) |

#### `columnTransformations` — Column transformations

```json
{
  "columnTransformations": [
    {
      "sourceColumn": "BookingDate",
      "transformations": [
        {
          "type": "dateformat",
          "fromFormat": "d.m.Y",
          "toFormat": "Y-m-d"
        }
      ],
      "outputColumn": "date",
      "outputAction": "overwrite"
    }
  ]
}
```

**outputAction:**

| Value | Behaviour |
|---|---|
| `overwrite` | Replace the target column with the transformation result (default) |
| `create` | Write the result into a new output column |
| `append` | Concatenate the result to the end of the existing column value. Add `"appendDelimiter": " "` (any string) to insert a separator between the existing and new value — the delimiter is omitted when the target column is still empty |
| `append-if-not-empty` | Same as `append` (including optional `appendDelimiter`) but skips entirely when the transformation result is empty — safe for optional values such as tags or notes lines |
| `append-line` | Same as `append` but the separator is always a newline `\n`; no leading newline when the target is empty |
| `overwrite-if-empty` | Only write the result if the target column is currently empty |
| `overwrite-if-not-empty` | Only write the result if the transformation result is not empty |

#### `directories` — File system

```json
{
  "directories": {
    "source": "/opt/ff-imp-preprocessor/import/source",
    "output": "/opt/ff-imp-preprocessor/import/output",
    "archive": "/opt/ff-imp-preprocessor/import/archive",
    "error": "/opt/ff-imp-preprocessor/import/error"
  }
}
```

| Field | Description |
| ------ | ----------- |
| `source` | Input directory |
| `output` | Output directory |
| `archive` | Archive for processed files |
| `error` | Error directory for invalid files |

#### `fireflyImport` — Firefly III integration

Optional. When present, passing `--do-import` to the `transform` command (or using `auto-import`) will call the Firefly III Data Importer after the output CSV is written.

See [Firefly III Integration](#firefly-iii-integration) for the full field reference and mode-specific examples.

---

## Transformation Types

There are **14 supported transformation types** that can be combined as a pipeline:

### 1. **trim** — Remove whitespace

Removes leading and trailing whitespace.

```json
{ "type": "trim" }
```

- Input: `  Coop Pronto  ` → Output: `Coop Pronto`

---

### 2. **lowercase** — Convert to lowercase

Converts to lowercase (UTF-8 safe).

```json
{ "type": "lowercase" }
```

- Input: `COOP PRONTO CHUR` → Output: `coop pronto chur`

---

### 3. **uppercase** — Convert to uppercase

Converts to uppercase (UTF-8 safe).

```json
{ "type": "uppercase" }
```

- Input: `Coop Pronto Chur` → Output: `COOP PRONTO CHUR`

---

### 4. **ucwordsfirst** — Capitalise after word separators

Capitalises the first letter after each word separator.

```json
{ "type": "ucwordsfirst" }
```

- `COOP PRONTO CHUR` → `Coop Pronto Chur`
- `migros-rail city` → `Migros-Rail City`
- `O'NEILL STORE` → `O'Neill Store`
- `SAINT-JEAN-DE-MAURIENNE` → `Saint-Jean-De-Maurienne`

Separators: space, hyphen, apostrophe, slash, period, comma, semicolon, colon, parentheses.

> **Guard:** If the input already contains *both* uppercase and lowercase letters (mixed-case), it is returned unchanged. This prevents accidentally re-casing intentionally formatted strings such as `"Coop pronto chur"`. Fully uppercase or fully lowercase inputs are always processed.

---

### 5. **replace** — String replacement

Replaces a substring with another string (case-sensitive).

```json
{ "type": "replace", "search": "  ", "replace": " " }
```

- Input: `Coop  Pronto` (two spaces) → Output: `Coop Pronto` (one space)

---

### 6. **split** — Split column

Splits a value at a delimiter and keeps a defined part.

```json
{ "type": "split", "delimiter": ";", "part": 0 }
```

- Input: `Coop Pronto Chur;7007 Chur` → Output: `Coop Pronto Chur`

---

### 7. **regex** — Regex replacement

Replaces parts of a string using a regular expression. Uses PHP `preg_replace`.

```json
{ "type": "regex", "pattern": "^(.*?);.*$", "replace": "$1" }
```

**No match → original value is passed through unchanged** (pipeline-safe).

Use capture groups as `$1`, `$2`, … in the `replace` field.
A pattern without `^`/`$` anchors replaces only the matched portion, not the whole value.

---

### 8. **regexextract** — Regex extraction

Extracts a capture group and returns **only that**. Uses PHP `preg_match`.

```json
{ "type": "regexextract", "pattern": "(\\d{4,} [^;]+)" }
```

- Input: `Coop Pronto Chur, 7007 Chur` → Output: `7007 Chur`
- No match → empty string

> **⚠ Not pipeline-safe:** A no-match discards all previous pipeline results. Use `regex` instead if you want to preserve the current value on no-match.

---

### 9. **dateformat** — Date reformatting

Converts between date formats.

```json
{ "type": "dateformat", "fromFormat": "d.m.Y", "toFormat": "Y-m-d" }
```

- Input: `10.12.2025` → Output: `2025-12-10`

Supports all PHP `DateTime` format characters.

---

### 10. **truncate** — Truncate string

Truncates a string to a maximum length.

```json
{ "type": "truncate", "maxLength": 100 }
```

---

### 11. **constantvalue** — Constant value from metadata

Injects an extracted metadata value as a constant for every row.

```json
{
  "sourceColumn": "_constant_",
  "transformations": [
    { "type": "constantvalue", "metadataKey": "account_iban" }
  ],
  "outputColumn": "account_iban",
  "outputAction": "create"
}
```

- Every row receives the extracted `account_iban` value (e.g. `CH9300777222666888999`) in a new column.

---

### 12. **map** — Copy / rename column

Copies a column value as-is (optionally to a new name).

```json
{ "type": "map" }
```

---

### 13. **pipeline** — Nested pipeline

Runs a sub-pipeline as a single transformation step.

```json
{
  "type": "pipeline",
  "steps": [
    { "type": "trim" },
    { "type": "lowercase" },
    { "type": "ucwordsfirst" }
  ]
}
```

Useful for grouping steps as a logical unit within a `transformations` array.

---

### 14. **timeperiod** — Map time to a period label

Parses a time string and returns the label of the matching period range.
Supports midnight-spanning ranges (e.g. 22:00–03:59).
Returns `default` (empty string by default) when no range matches or the input is invalid.

```json
{
  "type": "timeperiod",
  "timeFormat": "H:i:s",
  "periods": [
    { "from": "04:00:00", "to": "08:59:59", "label": "Morgen" },
    { "from": "09:00:00", "to": "10:59:59", "label": "Vormittag" },
    { "from": "11:00:00", "to": "13:59:59", "label": "Mittag" },
    { "from": "14:00:00", "to": "17:59:59", "label": "Nachmittag" },
    { "from": "18:00:00", "to": "21:59:59", "label": "Abend" },
    { "from": "22:00:00", "to": "03:59:59", "label": "Nacht" }
  ],
  "default": ""
}
```

- `"09:30:00"` → `"Vormittag"`
- `"23:00:00"` → `"Nacht"` (midnight-spanning range)
- `"02:00:00"` → `"Nacht"` (midnight-spanning range)
- `""` or unparseable input → `""`

`timeFormat` follows PHP's `DateTime::createFromFormat` syntax (default `H:i:s`).

---

### Row filtering — `skipIf`

Rows can be excluded from the output by adding a top-level `skipIf` key to the configuration.
The value is a filter node — either a bare condition or a nested `and`/`or` group.

**Bare condition:**

```json
"skipIf": { "column": "Buchungstext", "operator": "equals", "value": "Saldovortrag" }
```

**AND group:**

```json
"skipIf": {
  "and": [
    { "column": "Beschreibung1", "operator": "empty" },
    { "column": "Beschreibung2", "operator": "empty" }
  ]
}
```

**Nested AND / OR:**

```json
"skipIf": {
  "or": [
    { "column": "Amount", "operator": "gt", "value": "10000" },
    {
      "and": [
        { "column": "Type", "operator": "equals", "value": "Saldo" },
        { "column": "Notes", "operator": "empty" }
      ]
    }
  ]
}
```

**Supported operators:**

| Operator | Matches when… |
|---|---|
| `empty` | column value is empty string |
| `not-empty` | column value is not empty |
| `equals` | column value equals `"value"` |
| `not-equals` | column value does not equal `"value"` |
| `contains` | column value contains `"value"` |
| `not-contains` | column value does not contain `"value"` |
| `matches` | column value matches regex `"pattern"` |
| `not-matches` | column value does not match regex `"pattern"` |
| `gt` | `(float) column > (float) value` |
| `gte` | `(float) column >= (float) value` |
| `lt` | `(float) column < (float) value` |
| `lte` | `(float) column <= (float) value` |

---

### Pipeline example

Multiple transformations chained:

```json
{
  "sourceColumn": "BookingText",
  "transformations": [
    { "type": "trim" },
    { "type": "replace", "search": "  ", "replace": " " },
    { "type": "lowercase" },
    { "type": "ucwordsfirst" }
  ],
  "outputColumn": "description",
  "outputAction": "overwrite"
}
```

**Processing:**

1. `"  COOP  PRONTO  "` → trim → `"COOP  PRONTO"`
2. `"COOP  PRONTO"` → replace → `"COOP PRONTO"`
3. `"COOP PRONTO"` → lowercase → `"coop pronto"`
4. `"coop pronto"` → ucwordsfirst → `"Coop Pronto"`

---

## CLI Reference

```bash
php bin/transformer.php <command> [input] [config] [options]
```

### Commands

| Command | Description |
| ------- | ----------- |
| `test` | Test run (up to 10 rows) |
| `transform` | Full transformation |
| `validate` | Validate configuration |
| `auto-import` | Directory monitoring |
| `help` | Show help |

### Options

| Option | Description |
| ------ | ----------- |
| `--debug`, `-d` | Enable debug mode |
| `--rows=N` | Max. N rows (`test` command) |
| `--output=FILE`, `-o` | Output path |
| `--do-import` | Import into Firefly III after transformation (`transform` only) |
| `--strict` | Strict validation |
| `--watch` | Continuous monitoring |
| `--interval=SEC` | Check interval in seconds (default: 60) |
| `--dry-run` | Simulation mode, no real operations |

---

## Debug Mode

```bash
php bin/transformer.php test input.csv config/config.json --debug
```

### Log categories

| Category | When |
| -------- | ---- |
| `transformer` | Start/end of transformation |
| `csv_reader` | While reading CSV |
| `metadata` | During metadata extraction |
| `metadata_warning` | On extraction problems |
| `transformation` | For each transformation step |
| `csv_writer` | While writing output CSV |

### Debug log output (JSON)

```json
{
  "success": true,
  "debug_logs": [
    {
      "timestamp": 1702200120.5432,
      "category": "transformer",
      "message": "Transformation started",
      "data": { "inputFile": "input.csv", "maxRows": 0 }
    },
    {
      "timestamp": 1702200120.5445,
      "category": "metadata",
      "message": "Extraction rule applied",
      "data": { "rule_name": "account_iban", "value": "CH93..." }
    }
  ]
}
```

---

## Firefly III Integration

The transformer can automatically import transformed files into Firefly III.
Three operating modes cover all typical deployment scenarios.

### Prerequisites (all modes)

**1. Create a Firefly III Data Importer JSON configuration file**

This file maps transformed CSV columns to Firefly III transaction fields (format v3).

Recommended approach: upload a sample CSV once in the Firefly III Data Importer Web UI, configure the column mapping there, then download the finished configuration. Alternatively, use `config/firefly-import-config.example.json` as a template and adjust `default_account` to your asset account ID.

**2. Choose an operating mode** — see sections below.

---

### `fireflyImport` field reference

| Field | Type | Description |
| --- | --- | --- |
| `mode` | string | Operating mode: `cli` \| `docker` \| `http` (default: `cli`) |
| `jsonConfig` | string | Path to the Firefly III Data Importer JSON config file (format v3). For `cli` and `http` modes the file must exist locally; relative paths are resolved from the **working directory** where `php bin/transformer.php` is invoked (typically the project root). For `docker` mode the path is **inside the container** — local existence is not checked. |
| `importerCommand` | string | Full CLI command *(modes: cli, docker)* |
| `importerUrl` | string | URL of the Data Importer *(mode: http)* |
| `personalSecret` | string | The `AUTO_IMPORT_SECRET` set on the importer server (min. 16 chars). Sent as `?secret=` URL query parameter. *(mode: http)* |
| `accessToken` | string | Firefly III Personal Access Token. Sent as `Authorization: Bearer` header. Required if not already set as `FIREFLY_III_ACCESS_TOKEN` in the importer environment. *(mode: http)* |
| `deleteAfterImport` | boolean | Delete transformed CSV after successful import |
| `chunkSize` | integer | Split the CSV into chunks of at most N data rows and import each chunk as a separate request. Prevents server-side timeouts on large files (rule of thumb: ~3–4 s/transaction for HTTP mode). `0` or absent = no chunking (default). Applies to all modes. |
| `chunkRetries` | integer | Number of additional import attempts per chunk after the first. On failure the importer retries up to this many times before aborting. `0` or absent = no retry (default). Only effective when `chunkSize > 0`. |
| `chunkRetryDelay` | integer | Pause in seconds before each chunk request after the first, and between retry attempts for the same failed chunk. Addresses both inter-chunk cooldown and retry back-off. `0` or absent = no pause (default). Only effective when `chunkSize > 0`. |
| `connectionTimeout` | integer | Maximum seconds to wait for the TCP connection to the importer to be established. Distinct from `timeout` (full transfer duration). Default: `10`. *(mode: http only)* |
| `timeout` | integer | Timeout in seconds per request (default: 300). For chunked imports this applies per chunk, not for the total run. |
| `environment` | object | Additional environment variables *(modes: cli, docker)* |

---

### Mode `cli` — Transformer and Firefly on the same server

Both the transformer and the Firefly III Data Importer run on the same server. The transformer calls the importer directly as a local command.

```json
"fireflyImport": {
  "mode": "cli",
  "jsonConfig": "/opt/firefly-data-importer/storage/configurations/ubs-import.json",
  "importerCommand": "php /opt/firefly-data-importer/artisan importer:import",
  "deleteAfterImport": false,
  "chunkSize": 50,
  "chunkRetries": 3,
  "chunkRetryDelay": 10,
  "timeout": 300,
  "environment": {
    "FIREFLY_III_URL": "https://localhost",
    "FIREFLY_III_ACCESS_TOKEN": "your-token-here"
  }
}
```

---

### Mode `docker` — Transformer local, Firefly in Docker

The transformer runs locally or in its own container; the Firefly III Data Importer runs in a Docker container. The transformer calls the importer via `docker exec`.

**Important:** The transformer's output directory must be mounted as a volume in the importer container. `jsonConfig` is the path **inside the container** (not a local path). Do not use the `-it` flag (no TTY).

Example `docker-compose.yml` for the importer:

```yaml
services:
  firefly-importer:
    image: fireflyiii/data-importer:latest
    volumes:
      - /opt/ff-imp-preprocessor/import:/import
    environment:
      - FIREFLY_III_URL=https://your-firefly.com
      - FIREFLY_III_ACCESS_TOKEN=your-token-here
      - CAN_POST_FILES=false
```

```json
"fireflyImport": {
  "mode": "docker",
  "jsonConfig": "/import/configs/ubs-import.json",
  "importerCommand": "docker exec firefly-importer php artisan importer:import",
  "deleteAfterImport": false,
  "chunkSize": 50,
  "chunkRetries": 3,
  "chunkRetryDelay": 10,
  "timeout": 300
}
```

The JSON config file must be available inside the container — either via a volume mount or `docker cp`:

```bash
docker cp ubs-import.json firefly-importer:/import/configs/ubs-import.json
```

---

### Mode `http` — Transformer local, Firefly importer on a remote server

The transformer runs locally; the Firefly III Data Importer is reachable over HTTP(S). The CSV and JSON configuration are sent as a multipart HTTP upload to the importer.

**Requirements on the importer server:**

```text
CAN_POST_FILES=true
AUTO_IMPORT_SECRET=<secret>  # at least 16 characters — set this as personalSecret in your config
```

**Local requirement:** PHP extension `ext-curl`

```json
"fireflyImport": {
  "mode": "http",
  "importerUrl": "https://importer.your-server.com",
  "personalSecret": "your-auto-import-secret-min-16-chars",
  "accessToken": "your-firefly-iii-personal-access-token",
  "jsonConfig": "config/ubs-import.json",
  "deleteAfterImport": false,
  "chunkSize": 50,
  "chunkRetries": 3,
  "chunkRetryDelay": 10,
  "connectionTimeout": 10,
  "timeout": 300
}
```

The transformer sends a `POST` request to `{importerUrl}/autoupload?secret={personalSecret}` with the CSV and JSON config as multipart form fields. The `accessToken` is sent as `Authorization: Bearer`. If `FIREFLY_III_ACCESS_TOKEN` is already set in the importer's environment, `accessToken` can be omitted.

---

### Server-side tuning

For large imports the bottleneck is usually the Firefly III Data Importer server, not the transformer. The settings below belong in the importer's environment (`.env` or `docker-compose.yml`):

| Setting | Recommended value | Notes |
|---|---|---|
| `PHP_MEMORY_LIMIT` | `512M` – `2048M` | Docker env var. Raise when PHP crashes with "Allowed memory size exhausted". |
| `CONNECTION_TIMEOUT` | `60` | Seconds to wait for TCP connect to Firefly III API. Default is ~31 s (π × 10). |
| `IGNORE_DUPLICATE_ERRORS` | `true` | Suppress duplicate-transaction warnings on repeated imports. |

**nginx reverse proxy** (if applicable):
```nginx
proxy_read_timeout  600s;   # must exceed the longest single-chunk import time
client_max_body_size 64M;   # must accommodate your largest chunk CSV
```

**Docker Compose** example:
```yaml
services:
  firefly-importer:
    environment:
      - PHP_MEMORY_LIMIT=1024M
      - CONNECTION_TIMEOUT=60
      - IGNORE_DUPLICATE_ERRORS=true
```

---

### Usage

```bash
# Transform only (no import)
php bin/transformer.php transform input.csv config/config.json

# Transform and import into Firefly III
php bin/transformer.php transform input.csv config/config.json --do-import

# Watch mode: transform and import automatically for each new CSV in source directory
php bin/transformer.php auto-import config/config.json --watch
```

---

## Architecture

### Components

```text
bin/transformer.php (CLI entry point)
  ↓
TransformerEngine (orchestration)
  ├─ ConfigurationLoader (load / validate config)
  ├─ CsvReader (read CSV)
  ├─ MetadataExtractor (metadata via regex)
  ├─ ColumnTransformer (apply transformations)
  ├─ CsvWriter (write CSV)
  ├─ FireflyImporter (Firefly III integration)
  └─ DebugLogger (debug logs)
```

### Data flow

```text
Input CSV
  ↓
CsvReader::readMetadataLines() → array of lines
  ↓
MetadataExtractor::extract() → {iban: "...", currency: "..."}
  ↓
CsvReader::readCsvData() → array of rows
  ↓
ColumnTransformer::transformRow() → transformed row (pipeline)
  ↓
CsvWriter::write() → output CSV
```

### Classes

| Class | Responsibility |
| ----- | -------------- |
| `TransformerEngine` | Orchestrates the entire workflow |
| `ConfigurationLoader` | Loads and validates JSON configuration |
| `CsvReader` | Reads CSV with metadata support |
| `MetadataExtractor` | Extracts metadata via regex |
| `ColumnTransformer` | Transforms columns (pipeline) |
| `CsvWriter` | Writes output CSV |
| `FireflyImporter` | Imports into Firefly III |
| `DebugLogger` | Static logger for debug output |

---

## Error Handling

### Common errors

#### "Input file not found"

```bash
# Check the file path
ls -la input.csv

# Use an absolute path if relative paths do not work
php bin/transformer.php transform /absolute/path/input.csv config.json
```

---

#### "Missing metadata: account_iban"

The IBAN could not be extracted — wrong regex or wrong line number.

```bash
# Inspect the first lines of the CSV
head -5 input.csv

# Validate with debug output
php bin/transformer.php validate config.json input.csv --debug
```

---

#### "Invalid JSON: …"

Syntax error in `config.json`.

```bash
php -r "json_decode(file_get_contents('config/config.json'), true) or die('JSON invalid');"
```

---

#### "Configuration: 'csvStructure.headerLine' required"

A required configuration field is missing.

```bash
diff config/config.json config/config.example.json
```

---

### Exception handling

```php
try {
    $result = $engine->transform($inputFile);
    if (!$result['success']) {
        echo "Error: " . $result['error'];
    }
} catch (Exception $e) {
    echo "Fatal error: " . $e->getMessage();
}
```

---

## Tips

### UTF-8 handling

The transformer uses UTF-8 safe functions throughout:

- `mb_strtolower()` instead of `strtolower()`
- `mb_strtoupper()` instead of `strtoupper()`
- `mb_strlen()` for correct character counting

Supported encodings: UTF-8, ISO-8859-1, CP1252.

### Regex tips

**Pattern without delimiters (auto-wrapped):**

```json
"pattern": "IBAN:\\s*([A-Z0-9 ]+)"
// becomes: /IBAN:\s*([A-Z0-9 ]+)/u
```

**With explicit flags:**

```json
"pattern": "/IBAN:\\s*([A-Z0-9 ]+)/iu"
// case-insensitive
```

### Performance

- **Optimised for:** up to 1 million rows
- **Typical file size:** 10–100 k rows

### Batch processing

```bash
#!/bin/bash
for file in import/source/*.csv; do
    php bin/transformer.php transform "$file" config/config.json
    if [ $? -eq 0 ]; then
        mv "$file" import/archive/
    else
        mv "$file" import/error/
    fi
done
```

---

## Version History

**v1.0.0 (03 May 2026)**

- ✅ Initial release
- ✅ 14 transformation types
- ✅ Metadata extraction via regex
- ✅ Debug mode
- ✅ Firefly III integration (cli / docker / http)
- ✅ Full documentation

---

**License:** GPL-3.0  
**Author:** PHP CSV Transformer Project  
**Repository:** [git.andare.ch/david.reindl/ff-imp-preprocessor](https://git.andare.ch/david.reindl/ff-imp-preprocessor)