{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "urn:mobilespec:L3.ui",
  "title": "UI Structure Schema (L3)",
  "type": "object",
  "required": ["screen"],
  "additionalProperties": false,

  "properties": {
    "screen": {
      "type": "object",
      "required": ["id", "layout"],
      "additionalProperties": false,
      "properties": {
        "id": {
          "type": "string",
          "pattern": "^[a-z][a-z0-9_]*$",
          "description": "Screen id (must match L2 screen.id)"
        },
        "context": {
          "type": "string",
          "pattern": "^[a-z][a-z0-9_]*$",
          "description": "Optional screen context (e.g. nearby, owned)"
        },
        "layoutVariant": {
          "type": "string",
          "enum": ["default", "custom", "fullscreen"],
          "default": "default",
          "description": "Screen layout variant"
        },
        "appBar": {
          "type": "object",
          "additionalProperties": false,
          "properties": {
            "variant": {
              "type": "string",
              "enum": ["default", "back", "close", "none"],
              "default": "back",
              "description": "AppBar variant (default=back with back button, use 'default' for entry screens like home)"
            }
          }
        },
        "bottomBar": {
          "type": "object",
          "additionalProperties": false,
          "properties": {
            "visible": {
              "type": "boolean",
              "default": true,
              "description": "Show bottom navigation bar"
            }
          }
        },
        "layout": {
          "$ref": "#/$defs/layout"
        }
      }
    }
  },

  "$defs": {
    "layout": {
      "type": "object",
      "required": ["type"],
      "additionalProperties": false,
      "properties": {
        "type": {
          "type": "string",
          "enum": ["column", "row", "stack", "grid", "adaptiveGrid"]
        },
        "children": {
          "type": "array",
          "items": {
            "$ref": "#/$defs/node"
          }
        },
        "props": {
          "type": "object",
          "additionalProperties": true,
          "description": "Layout-level configuration (e.g. columns, gap)"
        }
      }
    },

    "node": {
      "type": "object",
      "required": ["component", "id", "name"],
      "additionalProperties": false,
      "properties": {
        "component": {
          "type": "string",
          "description": "Component type name (e.g. AppBar, HomeCard)"
        },
        "id": {
          "type": "string",
          "pattern": "^[a-z][a-z0-9_]*$"
        },
        "name": {
          "type": "string",
          "description": "Japanese display name (i18n source)"
        },

        "layout": {
          "$ref": "#/$defs/layout"
        },

        "children": {
          "type": "array",
          "items": {
            "$ref": "#/$defs/node"
          }
        },

        "props": {
          "type": "object",
          "additionalProperties": true
        },

        "action": {
          "type": "string",
          "pattern": "^[a-z][a-z0-9_]*$",
          "description": "Reference to L2 transition.id"
        },

        "fixed": {
          "type": "boolean",
          "description": "Fixed position (e.g. BottomBar)"
        },

        "repeatFrom": {
          "type": "string",
          "pattern": "^[a-z][a-z0-9_]*$",
          "description": "Repeat source key from L4 state"
        },

        "visibleWhen": {
          "type": "string",
          "pattern": "^[a-z][a-z0-9_]*$",
          "description": "Visibility condition key (evaluated in L4)"
        }
      }
    }
  }
}