schema {
    query: Query
    mutation: Mutation
}

"An object with an ID."
interface Node {
    "ID of the object."
    id: ID!
}

type Query {
    themes(
        "Returns a list of themes"
        after: String,
        "Returns the elements in the list that come before the specified cursor."
        before: String,
        "Returns the first _n_ elements from the list."
        first: Int,
        "Returns the last _n_ elements from the list."
        last: Int
    ): ThemeConnection!

    lessons(
        "Filter by the theme id. If missing, we return all lessons"
        themeId: ID,

        "Returns a list of themes"
        after: String,
        "Returns the elements in the list that come before the specified cursor."
        before: String,
        "Returns the first _n_ elements from the list."
        first: Int,
        "Returns the last _n_ elements from the list."
        last: Int
    ): LessonConnection!

    step(
        "Filter by the theme id. If missing, we return all lessons"
        stepId: ID!
    ): StepUnion!
}

type Mutation {
    lessonSave(input: LessonSaveInput!): LessonSavePayload

    "Used to complete a SlideStep and an ExerciseSummaryStep"
    stepComplete(input: StepCompleteInput!): StepCompletePayload

    "Used to complete a ExerciseStep"
    stepSubmitAnswer(input: StepSubmitAnswerInput!): StepSubmitAnswerPayload
}

# QUERY ==================================================
"The connection type for Theme."
type ThemeConnection {
    "Amount of records for this edge"
    count: Int!
    "A list of edges."
    edges: [ThemeEdge]
    "A list of nodes."
    nodes: [Theme]
    "Information to aid in pagination."
    pageInfo: PageInfo!
}

"The connection type for Theme."
type LessonConnection {
    "Amount of records for this edge"
    count: Int!
    "A list of edges."
    edges: [LessonEdge]
    "A list of nodes."
    nodes: [Lesson]
    "Information to aid in pagination."
    pageInfo: PageInfo!
}

"Information about pagination in a connection."
type PageInfo {
    "When paginating forwards, the cursor to continue."
    endCursor: String
    "When paginating forwards, are there more items?"
    hasNextPage: Boolean!
    "When paginating backwards, are there more items?"
    hasPreviousPage: Boolean!
    "When paginating backwards, the cursor to continue."
    startCursor: String
}

"An edge in a connection."
type ThemeEdge {
    "A cursor for use in pagination."
    cursor: String!
    "The item at the end of the edge."
    node: Theme
}

"An edge in a connection."
type LessonEdge {
    "A cursor for use in pagination."
    cursor: String!
    "The item at the end of the edge."
    node: Lesson
}

# INPUTS ================================================

input LessonSaveInput {
    lessonId: ID!
}

input StepCompleteInput {
    stepId: ID!
}

input StepSubmitAnswerInput {
    stepId: ID!
    answerIds: [ID!]
}

# TYPES ================================================

"A grouping of Lessons"
type Theme implements Node {
    id: ID!
    title: String!
    thumbnail: Image!
}

type Image {
    description: String!
    url: String!
}

enum DurationUnit {
    HOURS
    MINUTES
}

type Duration {
    value: Int!
    unit: DurationUnit!
    displayValue: String!
}

type Lesson implements Node {
    id: ID!
    title: String!
    thumbnail: Image!
    theme: Theme!
    duration: Duration!
}

# TODO: Decide to have LessonStatus exported as a Separate Query or extend the Lessson Type

type LessonStatus {
    percentComplete: Int!
    currentStep: StepUnion!
}

type LessonSavePayload {
    lesson: Lesson!
}

type StepCompletePayload {
    step: StepUnion!
    lesonStatus: LessonStatus!
}

type StepSubmitAnswerPayload {
    step: StepUnion!
    lesonStatus: LessonStatus!
}

interface LessonStep {
    "ID of the object."
    id: ID!
}

enum AnswerStatus {
    CORRECT
    INCORRECT
    NONE
}

type AnswerResult {
    answer: Answer!
    status: AnswerStatus!
}

type SlideStep implements LessonStep {
    id: ID!
    title: String!
    previousStep: StepUnion

    image: Image
    description: String!
}

type ExerciseStep implements LessonStep {
    id: ID!
    title: String!

    question: String!
    answers: [Answer]
}

type Answer {
    id: ID!
    title: String!
}

type LessonSummaryStep implements LessonStep {
    id: ID!

    experiencePoints: Int!
}

type ExerciseSummaryStep implements LessonStep {
    id: ID!

    results: [AnswerResult!]
}

union StepUnion = SlideStep | ExerciseStep | ExerciseSummaryStep | LessonSummaryStep

  scalar Upload

  type File {
    filename: String!
    mimetype: String!
    encoding: String!
  }

  type Mutation {
    singleUpload(file: Upload!): File!
  }

type LessonStatus {
    percentComplete: Int!
    currentStep: StepUnion!
}

mutation themeCreate(input: ThemeCreateInput!)

type ThemeCreateInput {
   title: String!
   thumbnailId: ID!
}

mutation themeUpdate(input: ThemeUpdateInput!)

type ThemeCreateInput {
   id: ID!
   title: String!
   thumbnailId: ID!
}