{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "https://stac-extensions.github.io/sar/v1.3.1/schema.json",
  "title": "SAR Extension",
  "description": "STAC SAR Extension for STAC Items and STAC Collections.",
  "type": "object",
  "required": [
    "stac_extensions"
  ],
  "properties": {
    "stac_extensions": {
      "type": "array",
      "contains": {
        "const": "https://stac-extensions.github.io/sar/v1.3.1/schema.json"
      }
    }
  },
  "oneOf": [
    {
      "$comment": "This is the schema for STAC Items. Remove this object if this extension only applies to Collections.",
      "type": "object",
      "required": [
        "type",
        "properties",
        "assets"
      ],
      "properties": {
        "type": {
          "const": "Feature"
        },
        "properties": {
          "allOf": [
            {
              "$ref": "#/definitions/fields"
            },
            {
              "$ref": "#/definitions/sar_polarizations_unique_in_props"
            }
          ]
        },
        "assets": {
          "$comment": "This validates the fields in Item Assets, but does not require them.",
          "type": "object",
          "additionalProperties": {
            "$ref": "#/definitions/fields"
          }
        }
      }
    },
    {
      "$comment": "This is the schema for STAC Collections.",
      "type": "object",
      "required": [
        "type"
      ],
      "properties": {
        "type": {
          "const": "Collection"
        }
      },
      "anyOf": [
        {
          "$comment": "This is the schema for the top-level fields in a Collection. Remove this if this extension does not define top-level fields for Collections.",
          "allOf": [
            {
              "$ref": "#/definitions/fields"
            },
            {
              "$ref": "#/definitions/sar_polarizations_unique_in_props"
            }
          ]
        },
        {
          "$comment": "This validates the fields in Collection Assets, but does not require them.",
          "required": [
            "assets"
          ],
          "properties": {
            "assets": {
              "type": "object",
              "not": {
                "additionalProperties": {
                  "not": {
                    "allOf": [
                      {
                        "$ref": "#/definitions/require_any_field"
                      },
                      {
                        "$ref": "#/definitions/fields"
                      }
                    ]
                  }
                }
              }
            }
          }
        },
        {
          "$comment": "This is the schema for the fields in Item Asset Definitions. It doesn't require any fields.",
          "required": [
            "item_assets"
          ],
          "properties": {
            "item_assets": {
              "type": "object",
              "not": {
                "additionalProperties": {
                  "not": {
                    "allOf": [
                      {
                        "$ref": "#/definitions/require_any_field"
                      },
                      {
                        "$ref": "#/definitions/fields"
                      }
                    ]
                  }
                }
              }
            }
          }
        },
        {
          "$comment": "This is the schema for the fields in Summaries. By default, only checks the existence of the properties, but not the schema of the summaries.",
          "required": [
            "summaries"
          ],
          "properties": {
            "summaries": {
              "$ref": "#/definitions/require_any_field"
            }
          }
        }
      ]
    }
  ],
  "definitions": {
    "require_any_field": {
      "$comment": "Please list all fields here so that we can force the existence of one of them in other parts of the schemas.",
      "anyOf": [
        {"required": ["sar:instrument_mode"]},
        {"required": ["sar:frequency_band"]},
        {"required": ["sar:center_frequency"]},
        {"required": ["sar:bandwidth"]},
        {"required": ["sar:polarizations"]},
        {"required": ["sar:product_type"]},
        {"required": ["sar:resolution_range"]},
        {"required": ["sar:resolution_azimuth"]},
        {"required": ["sar:pixel_spacing_range"]},
        {"required": ["sar:pixel_spacing_azimuth"]},
        {"required": ["sar:looks_range"]},
        {"required": ["sar:looks_azimuth"]},
        {"required": ["sar:looks_equivalent_number"]},
        {"required": ["sar:observation_direction"]},
        {"required": ["sar:relative_burst"]},
        {"required": ["sar:beam_ids"]}
      ]
    },
    "fields": {
      "$comment": "Add your new fields here. Don't require them here, do that above in the item schema.",
      "type": "object",
      "properties": {
        "sar:instrument_mode": {
          "title": "Instrument Mode",
          "type": "string",
          "examples": [
            "WV"
          ],
          "minLength": 1
        },
        "sar:frequency_band": {
          "title": "Frequency Band",
          "type": "string",
          "enum": [
            "P",
            "L",
            "S",
            "C",
            "X",
            "Ku",
            "K",
            "Ka"
          ]
        },
        "sar:center_frequency": {
          "title": "Center Frequency (GHz)",
          "type": "number",
          "minimumExclusive": 0
        },
        "sar:bandwidth": {
          "title": "Range Bandwidth (GHz)",
          "type": "number",
          "minimumExclusive": 0
        },
        "sar:polarizations": {
          "$ref": "#/definitions/sar_polarizations"
        },
        "sar:product_type": {
          "title": "Product type",
          "type": "string",
          "minLength": 1,
          "examples": [
            "SSC",
            "MGD",
            "SGC"
          ]
        },
        "sar:resolution_range": {
          "title": "Resolution range (m)",
          "type": "number",
          "minimum": 0
        },
        "sar:resolution_azimuth": {
          "title": "Resolution azimuth (m)",
          "type": "number",
          "minimum": 0
        },
        "sar:pixel_spacing_range": {
          "title": "Pixel spacing range (m)",
          "type": "number",
          "minimum": 0
        },
        "sar:pixel_spacing_azimuth": {
          "title": "Pixel spacing azimuth (m)",
          "type": "number",
          "minimum": 0
        },
        "sar:looks_range": {
          "title": "Looks range",
          "type": "integer",
          "minimum": 0
        },
        "sar:looks_azimuth": {
          "title": "Looks azimuth",
          "type": "integer",
          "minimum": 0
        },
        "sar:looks_equivalent_number": {
          "title": "Equivalent number of looks (ENL)",
          "type": "number",
          "minimum": 0
        },
        "sar:observation_direction": {
          "title": "Antenna pointing direction",
          "type": "string",
          "enum": [
            "left",
            "right"
          ]
        },
        "sar:relative_burst": {
          "title": "Relative burst number",
          "type": "integer",
          "minimum": 1
        },
        "sar:beam_ids": {
          "title": "Beam identifiers",
          "type": "array",
          "items": {
            "type": "string"
          }
        }
      },
      "patternProperties": {
        "^(?!sar:)": {
          "$comment": "Do not allow unspecified fields prefixed with sar:"
        }
      },
      "additionalProperties": false
    },
    "sar_polarizations": {
      "title": "Polarizations",
      "type": "array",
      "minItems": 1,
      "items": {
        "type": "string",
        "enum": [
          "HH",
          "VV",
          "HV",
          "VH",
          "LH",
          "LV",
          "RH",
          "RV",
          "CH",
          "CV"
        ]
      }
    },
    "sar_polarizations_unique_in_props": {
      "type": "object",
      "properties": {
        "sar:polarizations": {
          "allOf": [
            {
              "$ref": "#/definitions/sar_polarizations"
            },
            {
              "type": "array",
              "uniqueItems": true
            }
          ]
        }
      }
    }
  }
}