{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "gno://schemas/changes@1.0",
  "title": "GNO Knowledge Changes",
  "type": "object",
  "required": ["schemaVersion", "changes", "page", "warnings"],
  "properties": {
    "schemaVersion": { "type": "string", "const": "1.0" },
    "changes": {
      "type": "array",
      "maxItems": 1000,
      "items": { "$ref": "#/definitions/change" }
    },
    "page": {
      "type": "object",
      "required": [
        "nextCursor",
        "earliestCursor",
        "latestCursor",
        "cursorExpired",
        "truncated",
        "retentionTruncated"
      ],
      "properties": {
        "nextCursor": { "type": ["string", "null"], "maxLength": 512 },
        "earliestCursor": {
          "type": "string",
          "minLength": 1,
          "maxLength": 512
        },
        "latestCursor": { "type": "string", "minLength": 1, "maxLength": 512 },
        "cursorExpired": { "type": "boolean" },
        "truncated": { "type": "boolean" },
        "retentionTruncated": { "type": "boolean" }
      },
      "additionalProperties": false
    },
    "warnings": { "type": "array", "items": { "type": "string" } }
  },
  "additionalProperties": false,
  "allOf": [
    {
      "if": {
        "properties": {
          "page": {
            "type": "object",
            "properties": { "cursorExpired": { "const": true } },
            "required": ["cursorExpired"]
          }
        },
        "required": ["page"]
      },
      "then": {
        "properties": {
          "changes": { "type": "array", "maxItems": 0 },
          "page": {
            "type": "object",
            "properties": {
              "nextCursor": { "type": "null" },
              "retentionTruncated": { "const": true }
            }
          }
        }
      }
    },
    {
      "if": {
        "properties": {
          "page": {
            "type": "object",
            "properties": { "truncated": { "const": true } },
            "required": ["truncated"]
          }
        },
        "required": ["page"]
      },
      "then": {
        "properties": {
          "page": {
            "type": "object",
            "properties": {
              "nextCursor": { "type": "string", "minLength": 1 }
            }
          }
        }
      },
      "else": {
        "properties": {
          "page": {
            "type": "object",
            "properties": { "nextCursor": { "type": "null" } }
          }
        }
      }
    }
  ],
  "definitions": {
    "snapshot": {
      "type": "object",
      "required": [
        "relPath",
        "docid",
        "uri",
        "sourceHash",
        "mirrorHash",
        "active"
      ],
      "properties": {
        "relPath": { "type": "string" },
        "docid": { "type": "string", "pattern": "^#[a-f0-9]{6,}$" },
        "uri": { "type": "string", "pattern": "^gno://.+" },
        "sourceHash": { "$ref": "#/definitions/sha256" },
        "mirrorHash": {
          "anyOf": [{ "$ref": "#/definitions/sha256" }, { "type": "null" }]
        },
        "active": { "type": "boolean" }
      },
      "additionalProperties": false
    },
    "setDelta": {
      "type": "object",
      "required": ["added", "removed"],
      "properties": {
        "added": {
          "type": "array",
          "maxItems": 16,
          "uniqueItems": true,
          "items": { "type": "string", "minLength": 1, "maxLength": 256 }
        },
        "removed": {
          "type": "array",
          "maxItems": 16,
          "uniqueItems": true,
          "items": { "type": "string", "minLength": 1, "maxLength": 256 }
        }
      },
      "additionalProperties": false
    },
    "dateDelta": {
      "type": "object",
      "required": ["added", "removed", "changed"],
      "properties": {
        "added": {
          "type": "array",
          "maxItems": 16,
          "uniqueItems": true,
          "items": { "type": "string", "minLength": 1, "maxLength": 256 }
        },
        "removed": {
          "type": "array",
          "maxItems": 16,
          "uniqueItems": true,
          "items": { "type": "string", "minLength": 1, "maxLength": 256 }
        },
        "changed": {
          "type": "array",
          "maxItems": 16,
          "uniqueItems": true,
          "items": { "type": "string", "minLength": 1, "maxLength": 256 }
        }
      },
      "additionalProperties": false
    },
    "structureDelta": {
      "type": "object",
      "required": ["headings", "links", "typedEdges", "dates", "truncated"],
      "properties": {
        "headings": { "$ref": "#/definitions/setDelta" },
        "links": { "$ref": "#/definitions/setDelta" },
        "typedEdges": { "$ref": "#/definitions/setDelta" },
        "dates": { "$ref": "#/definitions/dateDelta" },
        "truncated": { "type": "boolean" }
      },
      "additionalProperties": false
    },
    "sha256": {
      "type": "string",
      "pattern": "^[a-f0-9]{64}$"
    },
    "change": {
      "type": "object",
      "required": [
        "id",
        "kind",
        "collection",
        "observedAt",
        "previous",
        "current",
        "structureDelta"
      ],
      "properties": {
        "id": { "type": "string", "minLength": 1, "maxLength": 512 },
        "kind": {
          "type": "string",
          "enum": ["create", "update", "rename", "inactivate", "reactivate"]
        },
        "collection": { "type": "string", "minLength": 1 },
        "observedAt": { "type": "string", "format": "date-time" },
        "previous": {
          "anyOf": [{ "$ref": "#/definitions/snapshot" }, { "type": "null" }]
        },
        "current": {
          "anyOf": [{ "$ref": "#/definitions/snapshot" }, { "type": "null" }]
        },
        "structureDelta": { "$ref": "#/definitions/structureDelta" }
      },
      "additionalProperties": false,
      "allOf": [
        {
          "if": {
            "properties": { "kind": { "const": "create" } },
            "required": ["kind"]
          },
          "then": {
            "properties": {
              "previous": { "type": "null" },
              "current": {
                "type": "object",
                "properties": { "active": { "const": true } },
                "required": ["active"]
              }
            }
          }
        },
        {
          "if": {
            "properties": { "kind": { "enum": ["update", "rename"] } },
            "required": ["kind"]
          },
          "then": {
            "properties": {
              "previous": { "$ref": "#/definitions/snapshot" },
              "current": { "$ref": "#/definitions/snapshot" }
            }
          }
        },
        {
          "if": {
            "properties": { "kind": { "const": "inactivate" } },
            "required": ["kind"]
          },
          "then": {
            "properties": {
              "previous": {
                "type": "object",
                "properties": { "active": { "const": true } },
                "required": ["active"]
              },
              "current": {
                "type": "object",
                "properties": { "active": { "const": false } },
                "required": ["active"]
              }
            }
          }
        },
        {
          "if": {
            "properties": { "kind": { "const": "reactivate" } },
            "required": ["kind"]
          },
          "then": {
            "properties": {
              "previous": {
                "type": "object",
                "properties": { "active": { "const": false } },
                "required": ["active"]
              },
              "current": {
                "type": "object",
                "properties": { "active": { "const": true } },
                "required": ["active"]
              }
            }
          }
        }
      ]
    }
  }
}