lex-conditioner

Conditional rule engine for LegionIO. Evaluates JSON-based rules against task payloads to determine whether downstream tasks should execute, enabling branching logic in task chains.

Installation

gem install lex-conditioner

Or add to your Gemfile:

gem 'lex-conditioner'

Standalone Client

Use the conditioner without the full LegionIO framework:

require 'legion/extensions/conditioner/client'

client = Legion::Extensions::Conditioner::Client.new

result = client.evaluate(
  conditions: { all: [
    { fact: 'response.code', operator: 'greater_or_equal', value: 200 },
    { fact: 'response.code', operator: 'less_than', value: 300 }
  ] },
  values: { response: { code: 200, body: 'OK' } }
)

result[:valid]       # => true
result[:explanation] # => { valid: true, group: :all, rules: [...] }

The explanation includes per-rule results with actual values:

result[:explanation][:rules]
# => [
#   { fact: "response.code", operator: "greater_or_equal", value: 200, actual: 200, result: true },
#   { fact: "response.code", operator: "less_than", value: 300, actual: 200, result: true }
# ]

Condition Format

Rules use all/any grouping with fact/operator/value entries. Facts use dot notation for nested keys.

{
  "all": [
    { "fact": "response.code", "operator": "greater_or_equal", "value": 200 },
    { "any": [
      { "fact": "action", "operator": "equal", "value": "opened" },
      { "fact": "action", "operator": "equal", "value": "reopened" }
    ]}
  ]
}

Operators

Binary (require fact + value)

Operator	Description
equal	Exact equality
not_equal	Inequality
greater_than	Numeric greater than
less_than	Numeric less than
greater_or_equal	Numeric greater than or equal
less_or_equal	Numeric less than or equal
between	Value within range (value is [min, max])
contains	String contains substring
starts_with	String starts with prefix
ends_with	String ends with suffix
matches	String matches regex pattern
in_set	Value is in the given array
not_in_set	Value is not in the given array
size_equal	Collection/string size equals value

Unary (require fact only)

Operator	Description
nil	Value is nil
not_nil	Value is not nil
is_true	Value is truthy
is_false	Value is falsy
is_string	Value is a String
is_array	Value is an Array
is_integer	Value is an Integer
empty	Value is nil or empty
not_empty	Value is present and not empty

Runners

Conditioner

check(conditions:, **payload)

Evaluates conditions against the payload. Routes to transformation or task queue based on result:

• Condition passes + transformation present: routes to task.subtask.transform
• Condition passes + routing key present: routes to runner_routing_key
• Condition fails: conditioner.failed, no dispatch

Transport

• Exchange: task (inherits from Legion::Transport::Exchanges::Task)
• Queue: task.conditioner
• Routing keys: task.subtask, task.subtask.conditioner

Requirements

• Ruby >= 3.4
• LegionIO framework (for AMQP actor mode)
• Standalone Client works without the framework

License

MIT