{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://schemas.fablepool.org/v1/content-document.json",
  "title": "FablePool Content Document",
  "description": "Structured, renderer-agnostic rich content format used for problem statements, hints, solutions, lesson prose, and review-anchored text. Designed to be compiled to MDX/HTML on the frontend, to degrade gracefully on low bandwidth (every widget carries a static fallback), and to be safely sanitised (no raw HTML).",
  "type": "object",
  "required": ["version", "blocks"],
  "additionalProperties": false,
  "properties": {
    "version": {
      "description": "Content document format version.",
      "const": 1
    },
    "blocks": { "$ref": "#/$defs/blockArray" }
  },
  "$defs": {
    "blockArray": {
      "type": "array",
      "maxItems": 500,
      "items": { "$ref": "#/$defs/block" }
    },
    "inlineArray": {
      "type": "array",
      "maxItems": 500,
      "items": { "$ref": "#/$defs/inline" }
    },
    "block": {
      "oneOf": [
        { "$ref": "#/$defs/paragraph" },
        { "$ref": "#/$defs/heading" },
        { "$ref": "#/$defs/mathBlock" },
        { "$ref": "#/$defs/codeBlock" },
        { "$ref": "#/$defs/image" },
        { "$ref": "#/$defs/list" },
        { "$ref": "#/$defs/table" },
        { "$ref": "#/$defs/callout" },
        { "$ref": "#/$defs/quote" },
        { "$ref": "#/$defs/widgetEmbed" },
        { "$ref": "#/$defs/divider" }
      ]
    },
    "paragraph": {
      "type": "object",
      "required": ["type", "children"],
      "additionalProperties": false,
      "properties": {
        "type": { "const": "paragraph" },
        "children": { "$ref": "#/$defs/inlineArray" }
      }
    },
    "heading": {
      "type": "object",
      "required": ["type", "level", "children"],
      "additionalProperties": false,
      "properties": {
        "type": { "const": "heading" },
        "level": { "type": "integer", "minimum": 1, "maximum": 4 },
        "children": { "$ref": "#/$defs/inlineArray" }
      }
    },
    "mathBlock": {
      "type": "object",
      "required": ["type", "latex"],
      "additionalProperties": false,
      "properties": {
        "type": { "const": "math" },
        "latex": { "type": "string", "minLength": 1, "maxLength": 5000 },
        "numbered": { "type": "boolean", "default": false },
        "label": {
          "type": "string",
          "maxLength": 64,
          "description": "Anchor label for cross-references, e.g. 'eq:pythagoras'."
        }
      }
    },
    "codeBlock": {
      "type": "object",
      "required": ["type", "code"],
      "additionalProperties": false,
      "properties": {
        "type": { "const": "code" },
        "language": {
          "type": "string",
          "pattern": "^[a-z0-9+#-]{1,30}$",
          "default": "text"
        },
        "code": { "type": "string", "maxLength": 20000 },
        "caption": { "type": "string", "maxLength": 300 },
        "highlight_lines": {
          "type": "array",
          "items": { "type": "integer", "minimum": 1 },
          "maxItems": 200
        }
      }
    },
    "image": {
      "type": "object",
      "required": ["type", "alt"],
      "additionalProperties": false,
      "oneOf": [
        { "required": ["asset"] },
        { "required": ["src"] }
      ],
      "properties": {
        "type": { "const": "image" },
        "asset": {
          "type": "string",
          "format": "uuid",
          "description": "MediaAsset id resolved by the platform; preferred over external src."
        },
        "src": {
          "type": "string",
          "pattern": "^(https://|/media/)",
          "maxLength": 2000,
          "description": "External or platform-relative URL. Only https or platform media paths."
        },
        "alt": {
          "type": "string",
          "maxLength": 1000,
          "description": "Required alternative text. Empty string only for purely decorative images."
        },
        "caption": { "$ref": "#/$defs/inlineArray" },
        "width": { "type": "integer", "minimum": 16, "maximum": 4096 }
      }
    },
    "list": {
      "type": "object",
      "required": ["type", "items"],
      "additionalProperties": false,
      "properties": {
        "type": { "const": "list" },
        "ordered": { "type": "boolean", "default": false },
        "items": {
          "type": "array",
          "minItems": 1,
          "maxItems": 200,
          "items": {
            "type": "object",
            "required": ["blocks"],
            "additionalProperties": false,
            "properties": {
              "blocks": { "$ref": "#/$defs/blockArray" }
            }
          }
        }
      }
    },
    "table": {
      "type": "object",
      "required": ["type", "rows"],
      "additionalProperties": false,
      "properties": {
        "type": { "const": "table" },
        "caption": { "type": "string", "maxLength": 300 },
        "header": { "$ref": "#/$defs/tableRow" },
        "rows": {
          "type": "array",
          "minItems": 1,
          "maxItems": 200,
          "items": { "$ref": "#/$defs/tableRow" }
        }
      }
    },
    "tableRow": {
      "type": "array",
      "minItems": 1,
      "maxItems": 30,
      "items": { "$ref": "#/$defs/inlineArray" }
    },
    "callout": {
      "type": "object",
      "required": ["type", "variant", "blocks"],
      "additionalProperties": false,
      "properties": {
        "type": { "const": "callout" },
        "variant": {
          "enum": ["note", "tip", "warning", "definition", "theorem", "lemma", "proof", "example"]
        },
        "title": { "type": "string", "maxLength": 200 },
        "blocks": { "$ref": "#/$defs/blockArray" }
      }
    },
    "quote": {
      "type": "object",
      "required": ["type", "blocks"],
      "additionalProperties": false,
      "properties": {
        "type": { "const": "quote" },
        "blocks": { "$ref": "#/$defs/blockArray" },
        "attribution": { "$ref": "#/$defs/inlineArray" }
      }
    },
    "widgetEmbed": {
      "type": "object",
      "required": ["type", "widget", "fallback"],
      "additionalProperties": false,
      "description": "Embeds a sandboxed interactive widget. Widgets are untrusted: they run in a sandboxed iframe and never have network access. A static fallback is mandatory for accessibility and low-bandwidth rendering.",
      "properties": {
        "type": { "const": "widget" },
        "widget": { "$ref": "#/$defs/slug" },
        "widget_version": {
          "type": "string",
          "pattern": "^\\d+(\\.\\d+){0,2}$",
          "description": "Pinned or major-only widget version, e.g. '1' or '1.4.2'."
        },
        "params": {
          "type": "object",
          "description": "Parameters validated against the widget manifest's params_schema."
        },
        "height": { "type": "integer", "minimum": 64, "maximum": 2048 },
        "fallback": {
          "$ref": "#/$defs/blockArray",
          "description": "Static content rendered when the widget cannot run."
        }
      }
    },
    "divider": {
      "type": "object",
      "required": ["type"],
      "additionalProperties": false,
      "properties": {
        "type": { "const": "divider" }
      }
    },
    "inline": {
      "oneOf": [
        { "$ref": "#/$defs/textInline" },
        { "$ref": "#/$defs/mathInline" },
        { "$ref": "#/$defs/linkInline" },
        { "$ref": "#/$defs/referenceInline" }
      ]
    },
    "textInline": {
      "type": "object",
      "required": ["type", "text"],
      "additionalProperties": false,
      "properties": {
        "type": { "const": "text" },
        "text": { "type": "string", "maxLength": 10000 },
        "marks": {
          "type": "array",
          "uniqueItems": true,
          "items": {
            "enum": ["bold", "italic", "code", "underline", "strikethrough", "subscript", "superscript"]
          }
        }
      }
    },
    "mathInline": {
      "type": "object",
      "required": ["type", "latex"],
      "additionalProperties": false,
      "properties": {
        "type": { "const": "math" },
        "latex": { "type": "string", "minLength": 1, "maxLength": 2000 }
      }
    },
    "linkInline": {
      "type": "object",
      "required": ["type", "href", "children"],
      "additionalProperties": false,
      "properties": {
        "type": { "const": "link" },
        "href": {
          "type": "string",
          "pattern": "^(https?://|/|#)",
          "maxLength": 2000
        },
        "children": {
          "type": "array",
          "minItems": 1,
          "maxItems": 100,
          "items": {
            "oneOf": [
              { "$ref": "#/$defs/textInline" },
              { "$ref": "#/$defs/mathInline" }
            ]
          }
        }
      }
    },
    "referenceInline": {
      "type": "object",
      "required": ["type", "kind", "id"],
      "additionalProperties": false,
      "description": "Internal cross-reference to another platform entity; resolved to a link at render time and preserved across OER export/import.",
      "properties": {
        "type": { "const": "ref" },
        "kind": { "enum": ["problem", "course", "lesson", "glossary", "user"] },
        "id": { "type": "string", "maxLength": 64 },
        "label": { "type": "string", "maxLength": 300 }
      }
    },
    "slug": {
      "type": "string",
      "pattern": "^[a-z0-9][a-z0-9_-]{0,63}$"
    }
  }
}