{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "https://pamoja.molex.cloud/schema/rules-1.json",
  "title": "pamoja rules",
  "description": "Rules between nodes: when one topic's reading crosses a line, drive an output or publish a message, and undo it once the reading comes back.",
  "type": "object",
  "additionalProperties": false,
  "required": ["rules"],
  "properties": {
    "$schema": {
      "type": "string",
      "pattern": "(^|/)rules-1\\.json$",
      "description": "The format the file is written in: this schema's address, or a copy of it by the same file name. An editor reads it to check the file as it is typed."
    },
    "rules": {
      "type": "array",
      "description": "The rules, checked against each reading in the order they are listed.",
      "items": { "$ref": "#/definitions/rule" }
    }
  },
  "definitions": {
    "rule": {
      "type": "object",
      "description": "One rule: a line through one topic's readings, and what to do as a reading crosses it and comes back.",
      "additionalProperties": false,
      "required": ["name", "when"],
      "anyOf": [
        { "required": ["then"], "properties": { "then": { "minItems": 1 } } },
        { "required": ["otherwise"], "properties": { "otherwise": { "minItems": 1 } } }
      ],
      "properties": {
        "name": {
          "type": "string",
          "pattern": "\\S",
          "description": "A name no other rule in the file has, such as water-when-dry. The engine reports it when the rule fires."
        },
        "when": {
          "$ref": "#/definitions/condition"
        },
        "then": {
          "type": "array",
          "description": "What to do once, the moment the condition becomes true.",
          "items": { "$ref": "#/definitions/action" }
        },
        "otherwise": {
          "type": "array",
          "description": "What to do once, the moment the condition stops holding.",
          "items": { "$ref": "#/definitions/action" }
        }
      }
    },
    "condition": {
      "type": "object",
      "description": "The line a topic's readings cross. It names one side, above or below.",
      "additionalProperties": false,
      "required": ["topic"],
      "oneOf": [
        { "required": ["above"] },
        { "required": ["below"] }
      ],
      "properties": {
        "topic": {
          "type": "string",
          "minLength": 1,
          "pattern": "^[^+#]+$",
          "description": "The topic whose readings are watched, exactly as the node publishes to it. One topic, so no + or # wildcards."
        },
        "above": {
          "type": "number",
          "description": "The condition holds while readings are above this line."
        },
        "below": {
          "type": "number",
          "description": "The condition holds while readings are below this line."
        },
        "hysteresis": {
          "type": "number",
          "minimum": 0,
          "default": 0,
          "description": "How far back past the line a reading must come for the condition to clear, so readings hovering at the line do not fire it over and over."
        }
      }
    },
    "action": {
      "description": "One thing a rule does: drive an output, or publish a message.",
      "oneOf": [
        {
          "type": "object",
          "title": "drive",
          "description": "Switches an output the program running the rules holds under this name.",
          "additionalProperties": false,
          "required": ["drive", "on"],
          "properties": {
            "drive": {
              "type": "string",
              "pattern": "\\S",
              "description": "The output's name, such as bed-valve."
            },
            "on": {
              "type": "boolean",
              "description": "true to switch it on, false to switch it off."
            }
          }
        },
        {
          "type": "object",
          "title": "publish",
          "description": "Publishes a message over the link the rules run on.",
          "additionalProperties": false,
          "required": ["publish", "payload"],
          "properties": {
            "publish": {
              "type": "string",
              "minLength": 1,
              "pattern": "^[^+#]+$",
              "description": "The topic to publish to. One topic, so no + or # wildcards."
            },
            "payload": {
              "type": "string",
              "description": "The text to publish."
            }
          }
        }
      ]
    }
  }
}