# Expression Syntax

This document describes the expression syntax used in the application.

## Basic Syntax

### Variables

- `value` - Current field value
- `val` - a wrapped `value` in a monad that introduces additional operations
- `field['fieldname']` - Access other fields
- `field.fieldname` - Alternative syntax for accessing fields

### Operators

#### Comparison Operators
- `==` - Equal
- `===` - Strict equal
- `!=` - Not equal
- `!==` - Strict not equal
- `<` - Less than
- `<=` - Less than or equal
- `>` - Greater than
- `>=` - Greater than or equal

#### Logical Operators
- `and` - Logical AND
- `or` - Logical OR
- `not` - Logical NOT
  - Can be used with parentheses to negate complex expressions
  - Example: `not (value contains '1970')` - Negates the result of the contains operation
  - ! important note: always use parentheses with `not`, as it may lead to unexpected results!

#### String Operators
- `~` - String concatenation
- `contains` - String contains
- `matches` - Regular expression matching

#### Ternary Operators
- `condition ? true_value : false_value` - Ternary conditional

## String Functions (monad)

- `val.upper()` - Convert to uppercase
- `val.lower()` - Convert to lowercase
- `val.split(delimiter)` - Split string into array
- `val.merge(delimiter)` - Join array elements with delimiter
- `val.eq(value)` - Compare equality
- `val.from(value)` - Transform value
- `val.value()` - Return the final value from monad

## Array Functions

- `array.value()[index]` - Access array element by index
- `array.last()` - Get last element of array

## Time Functions

### Time Formatting

- `time.format(datetime, format, [timezone])` - Format datetime
  - Example: `time.format('2024-08-27T15:25:02.001Z', 'H:i')`
  - Example with timezone: `time.format('2024-08-27T15:25:02.001Z', 'H:i', 'Europe/Warsaw')`

### Time Duration Formatting

- `time.formatSeconds(seconds, format, [default])` - Format seconds as duration
  - Example: `time.formatSeconds(value + 220, 'M:S')`
  - Formats: 'M:S', 'S', 's'

## Examples

### String Manipulation
```
val.upper()                                  // Convert to uppercase
val.split('/').merge('|').upper()            // Split, join with new delimiter, uppercase
```

### Conditional Logic
```
field['null_val'] === null ? 'less 0' : 'more than 0'
value !== null and not (value contains '1970') ? time.format(value, 'U') * 1000 : null
```

### Time Formatting
```
time.formatSeconds(value + 220, 'M:S')       // Format seconds as minutes:seconds
time.format('2024-08-27T15:25:02.001Z', 'H:i', 'Europe/Warsaw')  // Format with timezone
```

### Field Access
```
field['field2']                              // Access other field
field.all_tmp.b_string                       // Nested field access
field.all_tmp.wrong ?? ''                    // With null coalescing
```