{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://schemas.fablepool.org/v1/course.schema.json",
  "title": "FablePool CourseVersion",
  "description": "Canonical storage format for one immutable version of a course: ordered modules containing lessons, problem sets, quizzes, and projects. Problems are referenced by id, never embedded, so they version and fork independently.",
  "type": "object",
  "required": ["schemaVersion", "kind", "title", "locale", "license", "modules"],
  "additionalProperties": false,
  "properties": {
    "schemaVersion": { "const": "1" },
    "kind": { "const": "course" },
    "courseId": { "type": "string", "format": "uuid" },
    "versionLabel": { "type": "string", "maxLength": 32 },
    "slug": { "type": "string", "pattern": "^[a-z0-9]+(?:-[a-z0-9]+)*$", "minLength": 3, "maxLength": 80 },
    "title": { "type": "string", "minLength": 3, "maxLength": 200 },
    "summary": { "type": "string", "maxLength": 500 },
    "description": { "$ref": "problem.schema.json#/$defs/RichContent" },
    "locale": { "type": "string", "pattern": "^[a-zA-Z]{2,3}(-[a-zA-Z0-9]{2,8})*$" },
    "translationOf": { "type": "string", "format": "uuid" },
    "license": { "type": "string", "enum": ["CC-BY-SA-4.0", "CC-BY-4.0", "CC0-1.0"] },
    "attribution": { "$ref": "problem.schema.json#/$defs/Attribution" },
    "tags": {
      "type": "array",
      "minItems": 1,
      "maxItems": 12,
      "uniqueItems": true,
      "items": { "type": "string", "pattern": "^[a-z0-9]+(?:-[a-z0-9]+)*$", "maxLength": 50 }
    },
    "topics": {
      "type": "array",
      "maxItems": 5,
      "uniqueItems": true,
      "items": { "type": "string", "pattern": "^[a-z0-9]+(?:-[a-z0-9]+)*$", "maxLength": 50 }
    },
    "difficulty": {
      "type": "object",
      "required": ["level"],
      "additionalProperties": false,
      "properties": {
        "level": { "type": "integer", "minimum": 1, "maximum": 5 },
        "label": { "type": "string", "enum": ["intro", "easy", "medium", "hard", "expert"] }
      }
    },
    "estimatedHours": { "type": "number", "exclusiveMinimum": 0, "maximum": 200 },
    "objectives": {
      "description": "Learner-facing outcomes: 'After this course you can …'.",
      "type": "array",
      "minItems": 1,
      "maxItems": 12,
      "items": { "type": "string", "maxLength": 300 }
    },
    "prerequisites": {
      "type": "array",
      "maxItems": 10,
      "items": { "$ref": "problem.schema.json#/$defs/Prerequisite" }
    },
    "coverAssetId": { "type": "string", "pattern": "^[a-zA-Z0-9_-]{8,64}$" },
    "assets": {
      "type": "array",
      "maxItems": 60,
      "items": { "$ref": "problem.schema.json#/$defs/AssetRef" }
    },
    "modules": {
      "type": "array",
      "minItems": 1,
      "maxItems": 30,
      "items": { "$ref": "#/$defs/Module" }
    },
    "completionPolicy": {
      "type": "object",
      "additionalProperties": false,
      "properties": {
        "requiredLessonFraction": {
          "description": "Fraction of required lessons that must be completed for course completion.",
          "type": "number",
          "minimum": 0.5,
          "maximum": 1,
          "default": 1
        },
        "requireFinalProject": { "type": "boolean", "default": false },
        "minQuizAverage": { "type": "number", "minimum": 0, "maximum": 1 }
      }
    },
    "changelog": { "type": "string", "maxLength": 2000 },
    "x-extensions": {
      "type": "object",
      "propertyNames": { "pattern": "^[a-z0-9-]+(\\.[a-z0-9-]+)+$" }
    }
  },
  "$defs": {
    "Module": {
      "type": "object",
      "required": ["id", "title", "lessons"],
      "additionalProperties": false,
      "properties": {
        "id": {
          "description": "Stable within the course family across versions, so Progress rows survive edits.",
          "type": "string",
          "pattern": "^[a-zA-Z0-9_-]{1,64}$"
        },
        "title": { "type": "string", "minLength": 1, "maxLength": 200 },
        "summary": { "type": "string", "maxLength": 500 },
        "unlockPolicy": {
          "description": "sequential: requires the previous module's required lessons; open: always available.",
          "type": "string",
          "enum": ["sequential", "open"],
          "default": "sequential"
        },
        "lessons": {
          "type": "array",
          "minItems": 1,
          "maxItems": 40,
          "items": { "$ref": "#/$defs/Lesson" }
        }
      }
    },
    "Lesson": {
      "type": "object",
      "required": ["id", "title", "lessonType", "items"],
      "additionalProperties": false,
      "properties": {
        "id": { "type": "string", "pattern": "^[a-zA-Z0-9_-]{1,64}$" },
        "title": { "type": "string", "minLength": 1, "maxLength": 200 },
        "lessonType": { "type": "string", "enum": ["lesson", "problem_set", "quiz", "project"] },
        "summary": { "type": "string", "maxLength": 500 },
        "required": {
          "description": "Counts toward course completion when true.",
          "type": "boolean",
          "default": true
        },
        "estimatedMinutes": { "type": "integer", "minimum": 1, "maximum": 480 },
        "items": {
          "type": "array",
          "minItems": 1,
          "maxItems": 60,
          "items": { "$ref": "#/$defs/LessonItem" }
        },
        "quizConfig": {
          "description": "Required when lessonType is 'quiz'; ignored otherwise.",
          "$ref": "#/$defs/QuizConfig"
        },
        "projectConfig": {
          "description": "Required when lessonType is 'project'; ignored otherwise.",
          "$ref": "#/$defs/ProjectConfig"
        }
      },
      "allOf": [
        {
          "if": { "properties": { "lessonType": { "const": "quiz" } }, "required": ["lessonType"] },
          "then": { "required": ["quizConfig"] }
        },
        {
          "if": { "properties": { "lessonType": { "const": "project" } }, "required": ["lessonType"] },
          "then": { "required": ["projectConfig"] }
        }
      ]
    },
    "LessonItem": {
      "oneOf": [
        {
          "description": "Expository content section rendered inline.",
          "type": "object",
          "required": ["itemType", "content"],
          "additionalProperties": false,
          "properties": {
            "itemType": { "const": "content" },
            "id": { "type": "string", "pattern": "^[a-zA-Z0-9_-]{1,64}$" },
            "content": { "$ref": "problem.schema.json#/$defs/RichContent" }
          }
        },
        {
          "description": "Reference to a problem. 'published-latest' tracks the problem's current published version; pinning a versionId freezes it (required inside quizzes for fairness).",
          "type": "object",
          "required": ["itemType", "problemId", "versionPolicy"],
          "additionalProperties": false,
          "properties": {
            "itemType": { "const": "problem" },
            "id": { "type": "string", "pattern": "^[a-zA-Z0-9_-]{1,64}$" },
            "problemId": { "type": "string", "format": "uuid" },
            "versionPolicy": {
              "oneOf": [
                {
                  "type": "object",
                  "required": ["mode"],
                  "additionalProperties": false,
                  "properties": { "mode": { "const": "published-latest" } }
                },
                {
                  "type": "object",
                  "required": ["mode", "versionId"],
                  "additionalProperties": false,
                  "properties": {
                    "mode": { "const": "pinned" },
                    "versionId": { "type": "string", "format": "uuid" }
                  }
                }
              ]
            },
            "weight": {
              "description": "Relative score weight inside quizzes/problem sets.",
              "type": "number",
              "exclusiveMinimum": 0,
              "maximum": 10,
              "default": 1
            },
            "optional": { "type": "boolean", "default": false }
          }
        }
      ]
    },
    "QuizConfig": {
      "type": "object",
      "required": ["passingScore"],
      "additionalProperties": false,
      "properties": {
        "passingScore": { "type": "number", "minimum": 0, "maximum": 1 },
        "attemptsAllowed": {
          "description": "0 means unlimited.",
          "type": "integer",
          "minimum": 0,
          "maximum": 10,
          "default": 0
        },
        "shuffleProblems": { "type": "boolean", "default": false },
        "timeLimitMinutes": { "type": "integer", "minimum": 1, "maximum": 480 },
        "showSolutionsAfter": {
          "type": "string",
          "enum": ["each_attempt", "pass", "exhausted_attempts", "never"],
          "default": "pass"
        }
      }
    },
    "ProjectConfig": {
      "type": "object",
      "required": ["brief", "submissionType"],
      "additionalProperties": false,
      "properties": {
        "brief": { "$ref": "problem.schema.json#/$defs/RichContent" },
        "submissionType": { "type": "string", "enum": ["free_text", "code", "url"] },
        "rubric": {
          "type": "array",
          "minItems": 1,
          "maxItems": 12,
          "items": {
            "type": "object",
            "required": ["criterion", "points"],
            "additionalProperties": false,
            "properties": {
              "criterion": { "type": "string", "maxLength": 300 },
              "points": { "type": "integer", "minimum": 1, "maximum": 50 },
              "description": { "type": "string", "maxLength": 1000 }
            }
          }
        },
        "gradingMode": {
          "type": "string",
          "enum": ["self_assess", "peer_review", "reviewer"],
          "default": "self_assess"
        },
        "peerReviewsRequired": { "type": "integer", "minimum": 1, "maximum": 5 }
      }
    }
  }
}