{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "Terrain heightmap metadata",
  "type": "object",
  "properties": {
    "schemaVersion": {
      "type": "number",
      "const": 1,
      "description": "Version of this file's layout. It changes only when the layout does."
    },
    "id": {
      "type": "string",
      "pattern": "^[a-z-]+$",
      "description": "Short id of the world, also its folder name under `data/maps`."
    },
    "world": {
      "type": "string",
      "minLength": 1,
      "description": "Name of the world (level) the terrain belongs to."
    },
    "gameBuild": {
      "type": "string",
      "description": "Steam build id the data was extracted from."
    },
    "units": {
      "type": "string",
      "const": "meters",
      "description": "Unit of every distance in the file."
    },
    "bounds": {
      "type": "object",
      "properties": {
        "min": {
          "type": "array",
          "prefixItems": [
            {
              "type": "number"
            },
            {
              "type": "number"
            }
          ],
          "items": false,
          "minItems": 2,
          "maxItems": 2,
          "description": "Minimum corner: [x, y] in meters."
        },
        "max": {
          "type": "array",
          "prefixItems": [
            {
              "type": "number"
            },
            {
              "type": "number"
            }
          ],
          "items": false,
          "minItems": 2,
          "maxItems": 2,
          "description": "Maximum corner: [x, y] in meters."
        }
      },
      "required": [
        "min",
        "max"
      ],
      "additionalProperties": false,
      "description": "Area the heightmap covers, as world X and Y. Pixel (0, 0) is the minimum corner."
    },
    "zRange": {
      "type": "object",
      "properties": {
        "min": {
          "type": "number",
          "description": "World Z in meters of pixel value 0."
        },
        "max": {
          "type": "number",
          "description": "World Z in meters of pixel value 65535."
        }
      },
      "required": [
        "min",
        "max"
      ],
      "additionalProperties": false,
      "description": "World Z of pixel value 0 and of pixel value 65535."
    },
    "heightmap": {
      "type": "object",
      "properties": {
        "file": {
          "type": "string",
          "const": "heightmap.png",
          "description": "File name inside the release's map folder."
        },
        "width": {
          "type": "integer",
          "exclusiveMinimum": 0,
          "maximum": 9007199254740991,
          "description": "Image width in pixels."
        },
        "height": {
          "type": "integer",
          "exclusiveMinimum": 0,
          "maximum": 9007199254740991,
          "description": "Image height in pixels."
        },
        "bitDepth": {
          "type": "number",
          "const": 16,
          "description": "Bits per pixel."
        },
        "metersPerPixel": {
          "type": "array",
          "prefixItems": [
            {
              "type": "number"
            },
            {
              "type": "number"
            }
          ],
          "items": false,
          "minItems": 2,
          "maxItems": 2,
          "description": "World meters per pixel along X and Y. Rows increase with world Y."
        },
        "encoding": {
          "type": "string",
          "const": "z = zRange.min + value / 65535 * (zRange.max - zRange.min)",
          "description": "How to turn a pixel value into a height."
        }
      },
      "required": [
        "file",
        "width",
        "height",
        "bitDepth",
        "metersPerPixel",
        "encoding"
      ],
      "additionalProperties": false,
      "description": "The 16-bit grayscale height image."
    },
    "check": {
      "type": "object",
      "properties": {
        "buildings": {
          "type": "integer",
          "minimum": 0,
          "maximum": 9007199254740991,
          "description": "Buildings used in the check."
        },
        "medianOffset": {
          "type": "number",
          "description": "Median offset in meters."
        },
        "p5Offset": {
          "type": "number",
          "description": "5th percentile offset in meters."
        },
        "p95Offset": {
          "type": "number",
          "description": "95th percentile offset in meters."
        },
        "fractionWithin5m": {
          "type": "number",
          "minimum": 0,
          "maximum": 1,
          "description": "Share of buildings whose base is within 5 m of the terrain."
        }
      },
      "required": [
        "buildings",
        "medianOffset",
        "p5Offset",
        "p95Offset",
        "fractionWithin5m"
      ],
      "additionalProperties": false,
      "description": "Self-check against the buildings: base of each building minus the terrain height under its centre."
    }
  },
  "required": [
    "schemaVersion",
    "id",
    "world",
    "gameBuild",
    "units",
    "bounds",
    "zRange",
    "heightmap",
    "check"
  ],
  "additionalProperties": false,
  "description": "Metadata for a world's baked terrain height image (a release asset, `heightmap.png`). All distances are meters."
}