typify_impl/

util.rs

// Copyright 2025 Oxide Computer Company

use std::collections::{BTreeMap, BTreeSet, HashSet};

use heck::ToPascalCase;
use log::debug;
use schemars::schema::{
    ArrayValidation, InstanceType, Metadata, ObjectValidation, Schema, SchemaObject, SingleOrVec,
    StringValidation, SubschemaValidation,
};
use unicode_ident::{is_xid_continue, is_xid_start};

use crate::{validate::schema_value_validate, Error, Name, RefKey, Result, TypeSpace};

pub(crate) fn metadata_description(metadata: &Option<Box<Metadata>>) -> Option<String> {
    metadata
        .as_ref()
        .and_then(|metadata| metadata.description.as_ref().cloned())
}

pub(crate) fn metadata_title(metadata: &Option<Box<Metadata>>) -> Option<String> {
    metadata
        .as_ref()
        .and_then(|metadata| metadata.title.as_ref().cloned())
}

pub(crate) fn metadata_title_and_description(metadata: &Option<Box<Metadata>>) -> Option<String> {
    metadata
        .as_ref()
        .and_then(|metadata| match (&metadata.title, &metadata.description) {
            (Some(t), Some(d)) => Some(format!("{}\n\n{}", t, d)),
            (Some(t), None) => Some(t.clone()),
            (None, Some(d)) => Some(d.clone()),
            (None, None) => None,
        })
}

/// Check if all schemas are mutually exclusive.
///
/// TODO This is used to turn an `anyOf` into a `oneOf` (i.e. if true). However
/// a better approach is probably to use the (newish) merge logic to try to
/// explode an `anyOf` into its 2^N possibilities. Some of those may be invalid
/// in which case we'll end up looking like a `oneOf`. The logic of merging is
/// conceptually identical to the logic below that validates **if** the schemas
/// **could** be merged (i.e. if they're compatible).
pub(crate) fn all_mutually_exclusive(
    subschemas: &[Schema],
    definitions: &BTreeMap<RefKey, Schema>,
) -> bool {
    let len = subschemas.len();
    // Consider all pairs
    (0..len - 1)
        .flat_map(|ii| (ii + 1..len).map(move |jj| (ii, jj)))
        .all(|(ii, jj)| {
            let a = resolve(&subschemas[ii], definitions);
            let b = resolve(&subschemas[jj], definitions);
            schemas_mutually_exclusive(a, b, definitions)
        })
}

/// This function needs to necessarily be conservative. We'd much prefer a
/// false negative than a false positive.
fn schemas_mutually_exclusive(
    a: &Schema,
    b: &Schema,
    definitions: &BTreeMap<RefKey, Schema>,
) -> bool {
    match (a, b) {
        // If either matches nothing then they are exclusive.
        (Schema::Bool(false), _) => true,
        (_, Schema::Bool(false)) => true,

        // If either matches anything then they are not exclusive.
        (Schema::Bool(true), _) => false,
        (_, Schema::Bool(true)) => false,

        // Iterate over subschemas.
        (
            other,
            Schema::Object(SchemaObject {
                metadata: None,
                instance_type: None,
                format: None,
                enum_values: None,
                const_value: None,
                subschemas: Some(subschemas),
                number: None,
                string: None,
                array: None,
                object: None,
                reference: None,
                extensions: _,
            }),
        )
        | (
            Schema::Object(SchemaObject {
                metadata: None,
                instance_type: None,
                format: None,
                enum_values: None,
                const_value: None,
                subschemas: Some(subschemas),
                number: None,
                string: None,
                array: None,
                object: None,
                reference: None,
                extensions: _,
            }),
            other,
        ) => match subschemas.as_ref() {
            // For an allOf, *any* subschema incompatibility means that the
            // schemas are mutually exclusive.
            SubschemaValidation {
                all_of: Some(s),
                any_of: None,
                one_of: None,
                not: None,
                if_schema: None,
                then_schema: None,
                else_schema: None,
            } => s
                .iter()
                .any(|sub| schemas_mutually_exclusive(sub, other, definitions)),

            // For a oneOf or anyOf, *all* subschemas need to be incompatible.
            SubschemaValidation {
                all_of: None,
                any_of: Some(s),
                one_of: None,
                not: None,
                if_schema: None,
                then_schema: None,
                else_schema: None,
            }
            | SubschemaValidation {
                all_of: None,
                any_of: None,
                one_of: Some(s),
                not: None,
                if_schema: None,
                then_schema: None,
                else_schema: None,
            } => s
                .iter()
                .all(|sub| schemas_mutually_exclusive(sub, other, definitions)),

            // For a not, they're mutually exclusive if they *do* match.
            SubschemaValidation {
                all_of: None,
                any_of: None,
                one_of: None,
                not: Some(sub),
                if_schema: None,
                then_schema: None,
                else_schema: None,
            } => !schemas_mutually_exclusive(sub, other, definitions),

            // Assume other subschemas are complex to understand and may
            // therefore be compatible.
            _ => false,
        },

        // If one schema has enumerated values, it's incompatible if all values
        // fail to validate against the other schema. (Conversely, if all
        // values *do* validate against the other schema, it simply seems
        // redundant--the most interesting case is if *some* values validate
        // and others do not.)
        (
            schema,
            Schema::Object(SchemaObject {
                instance_type: None,
                enum_values: Some(enum_values),
                ..
            }),
        )
        | (
            Schema::Object(SchemaObject {
                instance_type: None,
                enum_values: Some(enum_values),
                ..
            }),
            schema,
        ) => enum_values
            .iter()
            .all(|value| schema_value_validate(schema, value, definitions).is_err()),

        // If one schema has a constant value, it's incompatible if that value
        // fails to validate against the other schema.
        (
            schema,
            Schema::Object(SchemaObject {
                const_value: Some(value),
                ..
            }),
        )
        | (
            Schema::Object(SchemaObject {
                const_value: Some(value),
                ..
            }),
            schema,
        ) => schema_value_validate(schema, value, definitions).is_err(),

        // Neither is a Schema::Bool; we need to look at the instance types.
        (Schema::Object(a), Schema::Object(b)) => {
            match (&a.instance_type, &b.instance_type) {
                // If either is None, assume we're dealing with a more complex
                // type and that they are not exclusive.
                (None, _) => false,
                (_, None) => false,

                // If each schema has a single type and they aren't the same
                // then the types must be mutually exclusive.
                (Some(SingleOrVec::Single(a_single)), Some(SingleOrVec::Single(b_single)))
                    if a_single != b_single =>
                {
                    true
                }

                // For two objects we need to check required properties and
                // additional properties to see if there exists an object that
                // could successfully be validated by either schema.
                (Some(SingleOrVec::Single(a_single)), Some(SingleOrVec::Single(b_single)))
                    if a_single == b_single && a_single.as_ref() == &InstanceType::Object =>
                {
                    if let (
                        SchemaObject {
                            metadata: _,
                            instance_type: _,
                            format: None,
                            enum_values: None,
                            const_value: None,
                            subschemas: None,
                            number: None,
                            string: None,
                            array: None,
                            object: Some(a_validation),
                            reference: None,
                            extensions: _,
                        },
                        SchemaObject {
                            metadata: _,
                            instance_type: _,
                            format: None,
                            enum_values: None,
                            const_value: None,
                            subschemas: None,
                            number: None,
                            string: None,
                            array: None,
                            object: Some(b_validation),
                            reference: None,
                            extensions: _,
                        },
                    ) = (a, b)
                    {
                        object_schemas_mutually_exclusive(a_validation, b_validation)
                    } else {
                        // Could check further, but we'll be conservative.
                        false
                    }
                }

                // For two objects we need to check required properties and
                // additional properties to see if there exists an object that
                // could successfully be validated by either schema.
                (Some(SingleOrVec::Single(a_single)), Some(SingleOrVec::Single(b_single)))
                    if a_single == b_single && a_single.as_ref() == &InstanceType::Array =>
                {
                    if let (
                        SchemaObject {
                            metadata: _,
                            instance_type: _,
                            format: None,
                            enum_values: None,
                            const_value: None,
                            subschemas: None,
                            number: None,
                            string: None,
                            array: Some(a_validation),
                            object: None,
                            reference: None,
                            extensions: _,
                        },
                        SchemaObject {
                            metadata: _,
                            instance_type: _,
                            format: None,
                            enum_values: None,
                            const_value: None,
                            subschemas: None,
                            number: None,
                            string: None,
                            array: Some(b_validation),
                            object: None,
                            reference: None,
                            extensions: _,
                        },
                    ) = (a, b)
                    {
                        array_schemas_mutually_exclusive(a_validation, b_validation, definitions)
                    } else {
                        // Could check further, but we'll be conservative.
                        false
                    }
                }

                // For other simple types, check if the single type is the same
                // or not.
                (Some(SingleOrVec::Single(a_single)), Some(SingleOrVec::Single(b_single))) => {
                    a_single != b_single
                }

                // For two schemas with lists of instance types, make sure that
                // all pairs differ.
                (Some(SingleOrVec::Vec(a_vec)), Some(SingleOrVec::Vec(b_vec))) => a_vec
                    .iter()
                    .all(|instance_type| !b_vec.contains(instance_type)),

                // If one is a single type and the other is a vec, it will
                // suffice for now to check that the single item is different
                // than all the items in the vec.
                (Some(SingleOrVec::Single(single)), Some(SingleOrVec::Vec(vec)))
                | (Some(SingleOrVec::Vec(vec)), Some(SingleOrVec::Single(single))) => {
                    !vec.contains(single)
                }
            }
        }
    }
}

// See if there are unique, required properties of each that cannot be present
// in the other. In other words, see if there are properties that would
// uniquely identify an objects as validating exclusively with one or the other
// (but not with both).
fn object_schemas_mutually_exclusive(
    a_validation: &ObjectValidation,
    b_validation: &ObjectValidation,
) -> bool {
    let ObjectValidation {
        required: a_required,
        properties: a_properties,
        ..
    } = a_validation;
    let ObjectValidation {
        required: b_required,
        properties: b_properties,
        ..
    } = b_validation;

    // No properties? Too permissive / insufficiently exclusive.
    if a_properties.is_empty() || b_properties.is_empty() {
        return false;
    }

    // Either set of required properties must not be a subset of the other's
    // properties i.e. if there's a property that *must* be in one of the two
    // objects, and *cannot* be in the other, a property whose presence or
    // absence determines which of the two objects is relevant.
    if !a_required.is_subset(&b_properties.keys().cloned().collect())
        || !b_required.is_subset(&a_properties.keys().cloned().collect())
    {
        true
    } else {
        // Even if all required properties of each is a permitted property of
        // the other, each may have required properties that have fixed values
        // that differ. This can happen in particular for internally or
        // adjacently tagged enums where the properties may be identical but
        // the value of the tag property will be unique.

        // Compute the set that consists of fixed-value properties--a
        // tuple of the property name and the fixed value. Note that we may
        // encounter objects that specify that a field is required, but do
        // *not* specify the field. That's ok, but we can't assure mutual
        // exclusivity.
        let aa = a_required
            .iter()
            .filter_map(|name| {
                let t = a_properties.get(name).unwrap();
                constant_string_value(t).map(|s| (name.clone(), s))
            })
            .collect::<HashSet<_>>();
        let bb = b_required
            .iter()
            .filter_map(|name| {
                let t = b_properties.get(name).unwrap();
                constant_string_value(t).map(|s| (name.clone(), s))
            })
            .collect::<HashSet<_>>();

        // True if neither is a subset of the other.
        !aa.is_subset(&bb) && !bb.is_subset(&aa)
    }
}

fn array_schemas_mutually_exclusive(
    a_validation: &ArrayValidation,
    b_validation: &ArrayValidation,
    definitions: &BTreeMap<RefKey, Schema>,
) -> bool {
    match (a_validation, b_validation) {
        // If one is an array with a single item type and the other is a tuple
        // of a fixed size with fixed item types, we could only see a conflict
        // if the single item was compatible with *all* types of the tuple.
        // It's therefore sufficient to see if it's exclusive with *any* of the
        // types of the tuple.
        (
            ArrayValidation {
                items: Some(SingleOrVec::Single(single)),
                additional_items: None,
                ..
            },
            ArrayValidation {
                items: Some(SingleOrVec::Vec(vec)),
                additional_items: None,
                max_items: Some(max_items),
                min_items: Some(min_items),
                unique_items: None,
                contains: None,
            },
        )
        | (
            ArrayValidation {
                items: Some(SingleOrVec::Vec(vec)),
                additional_items: None,
                max_items: Some(max_items),
                min_items: Some(min_items),
                unique_items: None,
                contains: None,
            },
            ArrayValidation {
                items: Some(SingleOrVec::Single(single)),
                additional_items: None,
                ..
            },
        ) if max_items == min_items && *max_items as usize == vec.len() => vec
            .iter()
            .any(|schema| schemas_mutually_exclusive(schema, single, definitions)),

        (aa, bb) => {
            // If min > max then these schemas are incompatible.
            match (&aa.max_items, &bb.min_items) {
                (Some(max), Some(min)) if min > max => return true,
                _ => (),
            }
            match (&bb.max_items, &aa.min_items) {
                (Some(max), Some(min)) if min > max => return true,
                _ => (),
            }

            match (&aa.items, &aa.max_items, &bb.items, &bb.max_items) {
                // If thee's a single item schema and it's mutually exclusive
                // then we're done.
                (Some(SingleOrVec::Single(a_items)), _, Some(SingleOrVec::Single(b_items)), _)
                    if schemas_mutually_exclusive(a_items, b_items, definitions) =>
                {
                    return true;
                }

                _ => (),
            }
            debug!(
                "giving up on mutual exclusivity check {} {}",
                serde_json::to_string_pretty(aa).unwrap(),
                serde_json::to_string_pretty(bb).unwrap(),
            );
            false
        }
    }
}

/// If this schema represents a constant-value string, return that string,
/// otherwise return None.
pub(crate) fn constant_string_value(schema: &Schema) -> Option<&str> {
    match schema {
        // Singleton, typed enumerated value.
        Schema::Object(SchemaObject {
            metadata: _,
            instance_type: Some(SingleOrVec::Single(single)),
            format: None,
            enum_values: Some(values),
            const_value: None,
            subschemas: None,
            number: None,
            string: None,
            array: None,
            object: None,
            reference: None,
            extensions: _,
        }) if single.as_ref() == &InstanceType::String && values.len() == 1 => {
            values.first().unwrap().as_str()
        }

        // Singleton, untyped enumerated value.
        Schema::Object(SchemaObject {
            metadata: _,
            instance_type: None,
            format: None,
            enum_values: Some(values),
            const_value: None,
            subschemas: None,
            number: None,
            string: None,
            array: None,
            object: None,
            reference: None,
            extensions: _,
        }) if values.len() == 1 => values.first().unwrap().as_str(),

        // Constant value.
        Schema::Object(SchemaObject {
            metadata: _,
            instance_type: Some(SingleOrVec::Single(single)),
            format: None,
            enum_values: None,
            const_value: Some(value),
            subschemas: None,
            number: None,
            string: None,
            array: None,
            object: None,
            reference: None,
            extensions: _,
        }) if single.as_ref() == &InstanceType::String => value.as_str(),

        // Constant, untyped value.
        Schema::Object(SchemaObject {
            metadata: _,
            instance_type: None,
            format: None,
            enum_values: None,
            const_value: Some(value),
            subschemas: None,
            number: None,
            string: None,
            array: None,
            object: None,
            reference: None,
            extensions: _,
        }) => value.as_str(),

        _ => None,
    }
}

fn decode_segment(segment: &str) -> String {
    segment.replace("~1", "/").replace("~0", "~")
}

pub(crate) fn ref_key(ref_name: &str) -> RefKey {
    if ref_name == "#" {
        RefKey::Root
    } else if let Some(idx) = ref_name.rfind('/') {
        let decoded_segment = decode_segment(&ref_name[idx + 1..]);

        RefKey::Def(decoded_segment)
    } else {
        panic!("expected a '/' in $ref: {}", ref_name)
    }
}

fn resolve<'a>(
    schema: &'a Schema,
    definitions: &'a std::collections::BTreeMap<RefKey, Schema>,
) -> &'a Schema {
    match schema {
        Schema::Bool(_) => schema,
        Schema::Object(SchemaObject {
            metadata: _,
            instance_type: None,
            format: None,
            enum_values: None,
            const_value: None,
            subschemas: None,
            number: None,
            string: None,
            array: None,
            object: None,
            reference: Some(ref_name),
            extensions: _,
        }) => definitions.get(&ref_key(ref_name)).unwrap(),
        Schema::Object(SchemaObject {
            reference: None, ..
        }) => schema,
        // TODO Not sure what this would mean...
        _ => todo!(),
    }
}

/// Determine if a schema has a name (potentially).
pub(crate) fn schema_is_named(schema: &Schema) -> Option<String> {
    let raw_name = match schema {
        Schema::Object(SchemaObject {
            metadata: _,
            instance_type: None,
            format: None,
            enum_values: None,
            const_value: None,
            subschemas: None,
            number: None,
            string: None,
            array: None,
            object: None,
            reference: Some(reference),
            extensions: _,
        }) => {
            let idx = reference.rfind('/')?;
            Some(reference[idx + 1..].to_string())
        }

        Schema::Object(SchemaObject {
            metadata: Some(metadata),
            ..
        }) if metadata.as_ref().title.is_some() => Some(metadata.as_ref().title.as_ref()?.clone()),

        Schema::Object(SchemaObject {
            metadata: _,
            instance_type: _,
            format: None,
            enum_values: None,
            const_value: None,
            subschemas: Some(subschemas),
            number: None,
            string: None,
            array: None,
            object: None,
            reference: None,
            extensions: _,
        }) => singleton_subschema(subschemas).and_then(schema_is_named),

        // Best-effort fallback for things with raw types that can be easily inferred
        Schema::Object(SchemaObject {
            instance_type: Some(SingleOrVec::Single(single)),
            format,
            ..
        }) => match (**single, format.as_deref()) {
            (_, Some(format)) => Some(format.to_pascal_case()),
            (InstanceType::Boolean, _) => Some("Boolean".to_string()),
            (InstanceType::Integer, _) => Some("Integer".to_string()),
            (InstanceType::Number, _) => Some("Number".to_string()),
            (InstanceType::String, _) => Some("String".to_string()),
            (InstanceType::Array, _) => Some("Array".to_string()),
            (InstanceType::Object, _) => Some("Object".to_string()),
            (InstanceType::Null, _) => Some("Null".to_string()),
        },

        _ => None,
    }?;

    Some(sanitize(&raw_name, Case::Pascal))
}

/// Return the object data or None if it's not an object (or doesn't conform to
/// the objects we know how to handle).
pub(crate) fn get_object(schema: &Schema) -> Option<(&Option<Box<Metadata>>, &ObjectValidation)> {
    match schema {
        // Object
        Schema::Object(SchemaObject {
            metadata,
            instance_type: Some(SingleOrVec::Single(single)),
            format: None,
            enum_values: None,
            const_value: None,
            subschemas: None,
            number: _,
            string: _,
            array: _,
            object: Some(validation),
            reference: None,
            extensions: _,
        }) if single.as_ref() == &InstanceType::Object
            && schema_none_or_false(&validation.additional_properties)
            && validation.max_properties.is_none()
            && validation.min_properties.is_none()
            && validation.pattern_properties.is_empty()
            && validation.property_names.is_none() =>
        {
            Some((metadata, validation.as_ref()))
        }
        // Object with no explicit type (but the proper validation)
        Schema::Object(SchemaObject {
            metadata,
            instance_type: None,
            format: None,
            enum_values: None,
            const_value: None,
            subschemas: None,
            number: None,
            string: None,
            array: None,
            object: Some(validation),
            reference: None,
            extensions: _,
        }) if schema_none_or_false(&validation.additional_properties)
            && validation.max_properties.is_none()
            && validation.min_properties.is_none()
            && validation.pattern_properties.is_empty()
            && validation.property_names.is_none() =>
        {
            Some((metadata, validation.as_ref()))
        }

        // Trivial (n == 1) subschemas
        Schema::Object(SchemaObject {
            metadata,
            instance_type: _,
            format: None,
            enum_values: None,
            const_value: None,
            subschemas: Some(subschemas),
            number: None,
            string: None,
            array: None,
            object: None,
            reference: None,
            extensions: _,
        }) => singleton_subschema(subschemas).and_then(|sub_schema| {
            get_object(sub_schema).map(|(m, validation)| match m {
                Some(_) => (metadata, validation),
                None => (&None, validation),
            })
        }),

        // None if the schema doesn't match the shape we expect.
        _ => None,
    }
}

// We infer from a Some(Schema::Bool(false)) or None value that either nothing
// or nothing of importance is in the additional properties.
fn schema_none_or_false(additional_properties: &Option<Box<Schema>>) -> bool {
    matches!(
        additional_properties.as_ref().map(Box::as_ref),
        None | Some(Schema::Bool(false))
    )
}

pub(crate) fn singleton_subschema(subschemas: &SubschemaValidation) -> Option<&Schema> {
    match subschemas {
        SubschemaValidation {
            all_of: Some(subschemas),
            any_of: None,
            one_of: None,
            not: None,
            if_schema: None,
            then_schema: None,
            else_schema: None,
        }
        | SubschemaValidation {
            all_of: None,
            any_of: Some(subschemas),
            one_of: None,
            not: None,
            if_schema: None,
            then_schema: None,
            else_schema: None,
        }
        | SubschemaValidation {
            all_of: None,
            any_of: None,
            one_of: Some(subschemas),
            not: None,
            if_schema: None,
            then_schema: None,
            else_schema: None,
        } if subschemas.len() == 1 => subschemas.first(),
        _ => None,
    }
}

pub(crate) enum Case {
    Pascal,
    Snake,
}

pub(crate) fn sanitize(input: &str, case: Case) -> String {
    use heck::{ToPascalCase, ToSnakeCase};
    let to_case = match case {
        Case::Pascal => str::to_pascal_case,
        Case::Snake => str::to_snake_case,
    };

    // If every case was special then none of them would be.
    let out = match input {
        "+1" => "plus1".to_string(),
        "-1" => "minus1".to_string(),
        _ => to_case(&input.replace("'", "").replace(|c| !is_xid_continue(c), "-")),
    };

    let prefix = to_case("x");

    let out = match out.chars().next() {
        None => prefix,
        Some(c) if is_xid_start(c) => out,
        Some(_) => format!("{}{}", prefix, out),
    };

    // Make sure the string is a valid Rust identifier.
    if accept_as_ident(&out) {
        out
    } else {
        format!("{}_", out)
    }
}

/// Return true if the string is a valid Rust identifier.
///
/// If this function returns false, typify adds a trailing underscore to it. For
/// example, `fn` becomes `fn_`.
pub fn accept_as_ident(ident: &str) -> bool {
    // Adapted from https://docs.rs/syn/2.0.114/src/syn/ident.rs.html#60-74. The
    // main change is adding `gen` to the list.
    match ident {
        "_" |
        // Based on https://doc.rust-lang.org/1.65.0/reference/keywords.html
        "abstract" | "as" | "async" | "await" | "become" | "box" | "break" |
        "const" | "continue" | "crate" | "do" | "dyn" | "else" | "enum" |
        "extern" | "false" | "final" | "fn" | "for" | "gen" | "if" | "impl" |
        "in" | "let" | "loop" | "macro" | "match" | "mod" | "move" | "mut" |
        "override" | "priv" | "pub" | "ref" | "return" | "Self" | "self" |
        "static" | "struct" | "super" | "trait" | "true" | "try" | "type" |
        "typeof" | "unsafe" | "unsized" | "use" | "virtual" | "where" |
        "while" | "yield" => false,
        _ => true,
    }
}

pub(crate) fn recase(input: &str, case: Case) -> (String, Option<String>) {
    let new = sanitize(input, case);
    let rename = if new == input {
        None
    } else {
        Some(input.to_string())
    };
    (new, rename)
}

pub(crate) fn unique<I, T>(items: I) -> bool
where
    I: IntoIterator<Item = T>,
    T: Eq + std::hash::Hash,
{
    let mut unique = HashSet::new();
    items.into_iter().all(|item| unique.insert(item))
}

pub(crate) fn get_type_name(type_name: &Name, metadata: &Option<Box<Metadata>>) -> Option<String> {
    let name = match (type_name, metadata_title(metadata)) {
        (Name::Required(name), _) => name.clone(),
        (Name::Suggested(name), None) => name.clone(),
        (_, Some(name)) => name,
        (Name::Unknown, None) => None?,
    };

    Some(sanitize(&name, Case::Pascal))
}

pub(crate) struct TypePatch {
    pub name: String,
    pub derives: BTreeSet<String>,
    pub attrs: BTreeSet<String>,
}

impl TypePatch {
    /// Creates a new TypePatch by resolving patches for the given type name.
    pub fn new(type_space: &TypeSpace, type_name: String) -> Self {
        match type_space.settings.patch.get(&type_name) {
            None => Self {
                name: type_name,
                derives: Default::default(),
                attrs: Default::default(),
            },

            Some(patch) => {
                let name = patch.rename.clone().unwrap_or(type_name);
                let derives = patch.derives.iter().cloned().collect();
                let attrs = patch.attrs.iter().cloned().collect();

                Self {
                    name,
                    derives,
                    attrs,
                }
            }
        }
    }
}

pub(crate) struct StringValidator {
    max_length: Option<u32>,
    min_length: Option<u32>,
    pattern: Option<regress::Regex>,
}

impl StringValidator {
    pub fn new(type_name: &Name, validation: Option<&StringValidation>) -> Result<Self> {
        let (max_length, min_length, pattern) =
            validation.map_or(Ok((None, None, None)), |validation| {
                let max = validation.max_length;
                let min = validation.min_length;
                let pattern = validation
                    .pattern
                    .as_ref()
                    .map(|pattern| {
                        regress::Regex::new(pattern).map_err(|e| Error::InvalidSchema {
                            type_name: type_name.clone().into_option(),
                            reason: format!("invalid pattern '{}' {}", pattern, e),
                        })
                    })
                    .transpose()?;
                Ok((max, min, pattern))
            })?;
        Ok(Self {
            max_length,
            min_length,
            pattern,
        })
    }

    pub fn is_valid<S: AsRef<str>>(&self, s: S) -> bool {
        self.max_length
            .as_ref()
            .is_none_or(|max| s.as_ref().len() as u32 <= *max)
            && self
                .min_length
                .as_ref()
                .is_none_or(|min| s.as_ref().len() as u32 >= *min)
            && self
                .pattern
                .as_ref()
                .is_none_or(|pattern| pattern.find(s.as_ref()).is_some())
    }
}

#[cfg(test)]
mod tests {
    use std::collections::BTreeMap;

    use schemars::{
        gen::{SchemaGenerator, SchemaSettings},
        schema::StringValidation,
        schema_for, JsonSchema,
    };

    use crate::{
        util::{decode_segment, sanitize, schemas_mutually_exclusive, Case},
        Name,
    };

    use super::StringValidator;

    #[test]
    fn test_non_exclusive_structs() {
        #![allow(dead_code)]

        #[derive(JsonSchema)]
        struct A {
            a: Option<()>,
            b: (),
        }

        #[derive(JsonSchema)]
        struct B {
            a: (),
            b: Option<()>,
        }

        let a = schema_for!(A).schema.into();
        let b = schema_for!(B).schema.into();

        assert!(!schemas_mutually_exclusive(&a, &b, &BTreeMap::new()));
        assert!(!schemas_mutually_exclusive(&b, &a, &BTreeMap::new()));
    }

    #[test]
    fn test_non_exclusive_oneof_subschema() {
        #![allow(dead_code)]

        #[derive(JsonSchema)]
        enum A {
            B(i32),
            C(i64),
        }

        let mut settings = SchemaSettings::default();
        settings.inline_subschemas = true;
        let gen = SchemaGenerator::new(settings);

        let a = gen.into_root_schema_for::<Vec<A>>().schema.into();

        assert!(!schemas_mutually_exclusive(&a, &a, &BTreeMap::new()));
    }

    #[test]
    fn test_unique_prop_structs() {
        #![allow(dead_code)]

        #[derive(JsonSchema)]
        struct A {
            a: Option<()>,
            b: (),
        }

        #[derive(JsonSchema)]
        struct B {
            a: (),
            b: Option<()>,
            c: (),
        }

        let a = schema_for!(A).schema.into();
        let b = schema_for!(B).schema.into();

        assert!(schemas_mutually_exclusive(&a, &b, &BTreeMap::new()));
        assert!(schemas_mutually_exclusive(&b, &a, &BTreeMap::new()));
    }

    #[test]
    fn test_exclusive_structs() {
        #![allow(dead_code)]

        #[derive(JsonSchema)]
        struct A {
            a: Option<()>,
            b: (),
            aa: (),
        }

        #[derive(JsonSchema)]
        struct B {
            a: (),
            b: Option<()>,
            bb: (),
        }

        let a = schema_for!(A).schema.into();
        let b = schema_for!(B).schema.into();

        assert!(schemas_mutually_exclusive(&a, &b, &BTreeMap::new()));
        assert!(schemas_mutually_exclusive(&b, &a, &BTreeMap::new()));
    }

    #[test]
    fn test_exclusive_simple_arrays() {
        let a = schema_for!(Vec<u32>).schema.into();
        let b = schema_for!(Vec<f32>).schema.into();

        assert!(schemas_mutually_exclusive(&a, &b, &BTreeMap::new()));
        assert!(schemas_mutually_exclusive(&b, &a, &BTreeMap::new()));
    }

    #[test]
    fn test_decode_segment() {
        assert_eq!(decode_segment("foo~1bar"), "foo/bar");
        assert_eq!(decode_segment("foo~0bar"), "foo~bar");
    }

    #[test]
    fn test_sanitize() {
        assert_eq!(sanitize("type", Case::Snake), "type_");
        assert_eq!(sanitize("ref", Case::Snake), "ref_");
        assert_eq!(sanitize("gen", Case::Snake), "gen_");
        assert_eq!(sanitize("gen", Case::Pascal), "Gen");
        assert_eq!(sanitize("+1", Case::Snake), "plus1");
        assert_eq!(sanitize("-1", Case::Snake), "minus1");
        assert_eq!(sanitize("@timestamp", Case::Pascal), "Timestamp");
        assert_eq!(sanitize("won't and can't", Case::Pascal), "WontAndCant");
        assert_eq!(
            sanitize(
                "urn:ietf:params:scim:schemas:extension:gluu:2.0:user_",
                Case::Pascal
            ),
            "UrnIetfParamsScimSchemasExtensionGluu20User"
        );
        assert_eq!(sanitize("Ipv6Net", Case::Snake), "ipv6_net");
        assert_eq!(sanitize("V6", Case::Pascal), "V6");
    }

    #[test]
    fn test_string_validation() {
        let permissive = StringValidator::new(&Name::Unknown, None).unwrap();
        assert!(permissive.is_valid("everything should be fine"));
        assert!(permissive.is_valid(""));

        let also_permissive = StringValidator::new(
            &Name::Unknown,
            Some(&StringValidation {
                max_length: None,
                min_length: None,
                pattern: None,
            }),
        )
        .unwrap();
        assert!(also_permissive.is_valid("everything should be fine"));
        assert!(also_permissive.is_valid(""));

        let eight = StringValidator::new(
            &Name::Unknown,
            Some(&StringValidation {
                max_length: Some(8),
                min_length: Some(8),
                pattern: None,
            }),
        )
        .unwrap();
        assert!(eight.is_valid("Shadrach"));
        assert!(!eight.is_valid("Meshach"));
        assert!(eight.is_valid("Abednego"));

        let ach = StringValidator::new(
            &Name::Unknown,
            Some(&StringValidation {
                max_length: None,
                min_length: None,
                pattern: Some("ach$".to_string()),
            }),
        )
        .unwrap();
        assert!(ach.is_valid("Shadrach"));
        assert!(ach.is_valid("Meshach"));
        assert!(!ach.is_valid("Abednego"));
    }
}