document {
    info {
        title "KDL Schema" lang="en"
        description "KDL Schema KDL schema in KDL" lang="en"
        author "Kat Marchán" {
            link "https://github.com/zkat" rel="self"
        }
        contributor "Lars Willighagen" {
            link "https://github.com/larsgw" rel="self"
        }
        link "https://github.com/zkat/kdl" rel="documentation"
        license "Creative Commons Attribution-ShareAlike 4.0 International License" spdx="CC-BY-SA-4.0" {
            link "https://creativecommons.org/licenses/by-sa/4.0/" lang="en"
        }
        published "2021-08-31"
        modified "2021-09-01"
    }
    node "document" {
        min 1
        max 1
        children id="node-children" {
            node "node-names" id="node-names-node" description="Validations to apply specifically to arbitrary node names" {
                children ref=r#"[id="validations"]"#
            }
            node "other-nodes-allowed" id="other-nodes-allowed-node" description="Whether to allow child nodes other than the ones explicitly listed. Defaults to 'false'." {
                max 1
                value {
                    min 1
                    max 1
                    type "boolean"
                }
            }
            node "tag-names" description="Validations to apply specifically to arbitrary type tag names" {
                children ref=r#"[id="validations"]"#
            }
            node "other-tags-allowed" description="Whether to allow child node tags other than the ones explicitly listed. Defaults to 'false'." {
                max 1
                value {
                    min 1
                    max 1
                    type "boolean"
                }
            }
            node "info" description="A child node that describes the schema itself." {
                children {
                    node "title" description="The title of the schema or the format it describes" {
                        value description="The title text" {
                            type "string"
                            min 1
                            max 1
                        }
                        prop "lang" id="info-lang" description="The language of the text" {
                            type "string"
                        }
                    }
                    node "description" description="A description of the schema or the format it describes" {
                        value description="The description text" {
                            type "string"
                            min 1
                            max 1
                        }
                        prop ref=r#"[id="info-lang"]"#
                    }
                    node "author" description="Author of the schema" {
                        value id="info-person-name" description="Person name" {
                            type "string"
                            min 1
                            max 1
                        }
                        prop "orcid" id="info-orcid" description="The ORCID of the person" {
                            type "string"
                            pattern r"\d{4}-\d{4}-\d{4}-\d{4}"
                        }
                        children {
                            node ref=r#"[id="info-link"]"#
                        }
                    }
                    node "contributor" description="Contributor to the schema" {
                        value ref=r#"[id="info-person-name"]"#
                        prop ref=r#"[id="info-orcid"]"#
                    }
                    node "link" id="info-link" description="Links to itself, and to sources describing it" {
                        value description="A URL that the link points to" {
                            type "string"
                            format "url" "irl"
                            min 1
                            max 1
                        }
                        prop "rel" description="The relation between the current entity and the URL" {
                            type "string"
                            enum "self" "documentation"
                        }
                        prop ref=r#"[id="info-lang"]"#
                    }
                    node "license" description="The license(s) that the schema is licensed under" {
                        value description="Name of the used license" {
                            type "string"
                            min 1
                            max 1
                        }
                        prop "spdx" description="An SPDX license identifier" {
                            type "string"
                        }
                        children {
                            node ref=r#"[id="info-link"]"#
                        }
                    }
                    node "published" description="When the schema was published" {
                        value description="Publication date" {
                            type "string"
                            format "date"
                            min 1
                            max 1
                        }
                        prop "time" id="info-time" description="A time to accompany the date" {
                            type "string"
                            format "time"
                        }
                    }
                    node "modified" description="When the schema was last modified" {
                        value description="Modification date" {
                            type "string"
                            format "date"
                            min 1
                            max 1
                        }
                        prop ref=r#"[id="info-time"]"#
                    }
                    node "version" description="The version number of this version of the schema" {
                        value description="Semver version number" {
                            type "string"
                            pattern r"^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$"
                            min 1
                            max 1
                        }
                    }
                }
            }
            node "tag" id="tag-node" description="A tag belonging to a child node of `document` or another node." {
                value description="The name of the tag. If a tag name is not supplied, the node rules apply to _all_ nodes belonging to the parent." {
                    type "string"
                    max 1
                }
                prop "description" description="A description of this node's purpose." {
                    type "string"
                }
                prop "id" description="A globally-unique ID for this node." {
                    type "string"
                }
                prop "ref" description="A globally unique reference to another node." {
                    type "string"
                    format "kdl-query"
                }
                children {
                    node ref=r#"[id="node-names-node"]"#
                    node ref=r#"[id="other-nodes-allowed-node"]"#
                    node ref=r#"[id="node-node"]"#
                }
            }
            node "node" id="node-node" description="A child node belonging either to `document` or to another `node`. Nodes may be anonymous." {
                value description="The name of the node. If a node name is not supplied, the node rules apply to _all_ nodes belonging to the parent." {
                    type "string"
                    max 1
                }
                prop "description" description="A description of this node's purpose." {
                    type "string"
                }
                prop "id" description="A globally-unique ID for this node." {
                    type "string"
                }
                prop "ref" description="A globally unique reference to another node." {
                    type "string"
                    format "kdl-query"
                }
                children {
                    node "prop-names" description="Validations to apply specifically to arbitrary property names" {
                        children ref=r#"[id="validations"]"#
                    }
                    node "other-props-allowed" description="Whether to allow properties other than the ones explicitly listed. Defaults to 'false'." {
                        max 1
                        value {
                            min 1
                            max 1
                            type "boolean"
                        }
                    }
                    node "min" description="minimum number of instances of this node in its parent's children." {
                        max 1
                        value {
                            min 1
                            max 1
                            type "number"
                        }
                    }
                    node "max" description="maximum number of instances of this node in its parent's children." {
                        max 1
                        value {
                            min 1
                            max 1
                            type "number"
                        }
                    }
                    node ref=r#"[id="value-tag-node"]"#
                    node "prop" id="prop-node" description="A node property key/value pair." {
                        value description="The property key." {
                            type "string"
                        }
                        prop "id" description="A globally-unique ID of this property." {
                            type "string"
                        }
                        prop "ref" description="A globally unique reference to another property node." {
                            type "string"
                            format "kdl-query"
                        }
                        prop "description" description="A description of this property's purpose." {
                            type "string"
                        }
                        children description="Property-specific validations." {
                            node "required" description="Whether this property is required if its parent is present." {
                                max 1
                                value {
                                    min 1
                                    max 1
                                    type "boolean"
                                }
                            }
                        }
                        children id="validations" description="General value validations." {
                            node "tag" id="value-tag-node" description="The tags associated with this value" {
                                max 1
                                children ref=r#"[id="validations"]"#
                            }
                            node "type" description="The type for this prop's value." {
                                max 1
                                value {
                                    min 1
                                    type "string"
                                }
                            }
                            node "enum" description="An enumeration of possible values" {
                                max 1
                                value description="Enumeration choices" {
                                    min 1
                                }
                            }
                            node "pattern" description="PCRE (Regex) pattern or patterns to test prop values against." {
                                value {
                                    min 1
                                    type "string"
                                }
                            }
                            node "min-length" description="Minimum length of prop value, if it's a string." {
                                max 1
                                value {
                                    min 1
                                    type "number"
                                }
                            }
                            node "max-length" description="Maximum length of prop value, if it's a string." {
                                max 1
                                value {
                                    min 1
                                    type "number"
                                }
                            }
                            node "format" description="Intended data format." {
                                max 1
                                value {
                                    min 1
                                    type "string"
                                    // https://json-schema.org/understanding-json-schema/reference/string.html#format
                                    enum "date-time" "date" "time" "duration" "decimal" "currency" "country-2" "country-3" "country-subdivision" "email" "idn-email" "hostname" "idn-hostname" "ipv4" "ipv6" "url" "url-reference" "irl" "irl-reference" "url-template" "regex" "uuid" "kdl-query" "i8" "i16" "i32" "i64" "u8" "u16" "u32" "u64" "isize" "usize" "f32" "f64" "decimal64" "decimal128"
                                }
                            }
                            node "%" description="Only used for numeric values. Constrains them to be multiples of the given number(s)" {
                                max 1
                                value {
                                    min 1
                                    type "number"
                                }
                            }
                            node ">" description="Only used for numeric values. Constrains them to be greater than the given number(s)" {
                                max 1
                                value {
                                    min 1
                                    max 1
                                    type "number"
                                }
                            }
                            node ">=" description="Only used for numeric values. Constrains them to be greater than or equal to the given number(s)" {
                                max 1
                                value {
                                    min 1
                                    max 1
                                    type "number"
                                }
                            }
                            node "<" description="Only used for numeric values. Constrains them to be less than the given number(s)" {
                                max 1
                                value {
                                    min 1
                                    max 1
                                    type "number"
                                }
                            }
                            node "<=" description="Only used for numeric values. Constrains them to be less than or equal to the given number(s)" {
                                max 1
                                value {
                                    min 1
                                    max 1
                                    type "number"
                                }
                            }
                        }
                    }
                    node "value" id="value-node" description="one or more direct node values" {
                        prop "id" description="A globally-unique ID of this value." {
                            type "string"
                        }
                        prop "ref" description="A globally unique reference to another value node." {
                            type "string"
                            format "kdl-query"
                        }
                        prop "description" description="A description of this property's purpose." {
                            type "string"
                        }
                        children ref=r#"[id="validations"]"#
                        children description="Node value-specific validations" {
                            node "min" description="minimum number of values for this node." {
                                max 1
                                value {
                                    min 1
                                    max 1
                                    type "number"
                                }
                            }
                            node "max" description="maximum number of values for this node." {
                                max 1
                                value {
                                    min 1
                                    max 1
                                    type "number"
                                }
                            }
                        }
                    }
                    node "children" id="children-node" {
                        prop "id" description="A globally-unique ID of this children node." {
                            type "string"
                        }
                        prop "ref" description="A globally unique reference to another children node." {
                            type "string"
                            format "kdl-query"
                        }
                        prop "description" description="A description of this these children's purpose." {
                            type "string"
                        }
                        children ref=r#"[id="node-children"]"#
                    }
                }
            }
            node "definitions" description="Definitions to reference in parts of the top-level nodes" {
                children {
                    node ref=r#"[id="node-node"]"#
                    node ref=r#"[id="value-node"]"#
                    node ref=r#"[id="prop-node"]"#
                    node ref=r#"[id="children-node"]"#
                    node ref=r#"[id="tag-node"]"#
                }
            }
        }
    }
}