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A policy template consists of policy code and a data contract. The policy code is written in rego, and contains the logic of the task evaluation returning true or false. The data contract runs arbitrary code, including api calls, to return custom data fields that can be used by the policy code. These 2 components together make a policy template. Below you will find a reference implementation for policy code, syntax and guides on how to write data contracts.

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Referencing Fields in the Data contract

# Policy parameters set on the policy client
data.params.attribute_policy_parameter1

# Data WASM attributes
# e.g., if your data WASM returns {attribute_wasm_data1: string}
data.data.attribute_datawasm_data1

# Intent attributes
input.from
input.to
input.value
input.decoded_function_arguments[0]   # Get first parameter in the data field
input.chain_id                        # String
input.function.name

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Reference Rego Implementation

# MockERC20 Token Buy Policy
# --------------------------------
#
# For more information see:
#   * Rego comparison to other systems: https://www.openpolicyagent.org/docs/latest/comparison-to-other-systems/
#   * Rego Iteration: https://www.openpolicyagent.org/docs/latest/#iteration

package mockerc20

# By default, deny requests
default allow := false

# Allow admins to do anything
allow if user_is_admin

# user_is_admin is true if sender is the admin
user_is_admin if {
    data.params.admin == input.from
}

# Allow the action if the user is granted permission
allow if {
    base_symbol == "BTC"
    price > amount_out
    quote_symbol == "USD"
    token == lower(whitelist_token.address)
    function_name == allowed_action.function_name
    token == lower(allowed_action.address)
    allowed_action.max_limit > amount_out
}

# Derived fields
function_name := input.function.name
token := input.decoded_function_arguments[0]
amount_out := to_number(input.decoded_function_arguments[1])
allowed_action := data.params.allowed_actions[input.chain_id]
whitelist_token := data.params.token_whitelist[input.chain_id]
base_symbol := data.data.base_symbol
price := to_number(data.data.price)
quote_symbol := data.data.quote_symbol

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Writing Policy Data Contracts

Policy data contracts are used to data from offchain sources. The source code can be written in Python, Javascript or Rust as long as its compiled into Web Assembly (WASM). See below for guides on how to write and integrate this data.

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Rego Policy Syntax Reference

Reference