{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://tranquiltech.solutions/kindling/schemas/kindling_message.schema.json",
  "title": "KindlingMessage",
  "description": "A native Kindling message envelope. v0.1 transport is structured email under the hood.",
  "type": "object",
  "required": ["schema_version", "message_id", "type", "sender", "recipient", "sent_at", "body"],
  "additionalProperties": false,
  "properties": {
    "schema_version": { "type": "string", "const": "0.1" },
    "message_id": {
      "type": "string",
      "description": "Globally unique message identifier."
    },
    "type": {
      "type": "string",
      "enum": ["handshake-request", "handshake-response", "intro", "reply", "withdrawal", "system"]
    },
    "in_reply_to": {
      "type": "string",
      "description": "If this message is a reply, the message_id it replies to."
    },
    "sender": {
      "type": "object",
      "required": ["identity", "verification_level"],
      "additionalProperties": false,
      "properties": {
        "identity": { "type": "string" },
        "display_name": { "type": "string" },
        "verification_level": {
          "type": "string",
          "enum": ["unverified", "email", "oauth", "curator-vouched", "cryptographic"]
        },
        "profile_url": { "type": "string", "format": "uri" }
      }
    },
    "recipient": {
      "type": "object",
      "required": ["identity"],
      "additionalProperties": false,
      "properties": {
        "identity": { "type": "string" },
        "profile_url": { "type": "string", "format": "uri" }
      }
    },
    "via_pool": {
      "type": "object",
      "description": "If the message was triggered through a Pool, the Pool's reference.",
      "additionalProperties": false,
      "properties": {
        "url": { "type": "string", "format": "uri" },
        "id": { "type": "string" },
        "name": { "type": "string" }
      }
    },
    "sent_at": { "type": "string", "format": "date-time" },
    "subject": {
      "type": "string",
      "description": "Optional human-facing subject line."
    },
    "body": {
      "type": "object",
      "required": ["content_type", "content"],
      "additionalProperties": false,
      "properties": {
        "content_type": {
          "type": "string",
          "enum": ["text/plain", "text/markdown"]
        },
        "content": { "type": "string" }
      }
    },
    "transport": {
      "type": "object",
      "description": "Transport-layer metadata. v0.1: email.",
      "additionalProperties": false,
      "properties": {
        "type": { "type": "string", "enum": ["email"] },
        "message_headers": {
          "type": "object",
          "additionalProperties": { "type": "string" }
        }
      }
    }
  }
}