sui-graphql-macros 0.3.1

//! Field path validation against the GraphQL schema and Rust types.
//!
//! Validates paths by matching:
//! - Schema: field existence and list types
//! - Type structure: `Option`/`Vec` nesting matches `?`/`[]` markers in the path
//!
//! Null markers (`?`) in the path must correspond to `Option` wrappers in the type,
//! and `[]` markers must correspond to `Vec` wrappers.

use std::fmt::Write;

use crate::path::ParsedPath;
use crate::schema::Schema;

/// Represents the nesting structure of `Option` and `Vec` in a field type.
#[derive(Debug, Clone, PartialEq)]
pub enum TypeStructure {
    /// A type that is neither `Option` nor `Vec` (e.g., `String`, `u64`)
    Plain,
    /// `Option<T>` wrapping an inner structure
    Optional(Box<TypeStructure>),
    /// `Vec<T>` wrapping an inner structure
    Vector(Box<TypeStructure>),
}

/// Analyze a `syn::Type` into a `TypeStructure`.
///
/// Note: Type detection uses simple name matching (e.g., `ident == "Option"`),
/// the same approach used by serde_derive. This works for standard library types
/// but won't distinguish custom types with the same name.
/// See: https://github.com/serde-rs/serde/blob/master/serde_derive/src/internals/attr.rs
pub fn analyze_type(ty: &syn::Type) -> TypeStructure {
    if let Some(inner) = unwrap_option(ty) {
        TypeStructure::Optional(Box::new(analyze_type(inner)))
    } else if let Some(inner) = unwrap_vec(ty) {
        TypeStructure::Vector(Box::new(analyze_type(inner)))
    } else {
        TypeStructure::Plain
    }
}

/// Returns the inner type if `ty` is `Option<T>`, otherwise `None`.
fn unwrap_option(ty: &syn::Type) -> Option<&syn::Type> {
    unwrap_type(ty, "Option")
}

/// Returns the inner type if `ty` is `Vec<T>`, otherwise `None`.
fn unwrap_vec(ty: &syn::Type) -> Option<&syn::Type> {
    unwrap_type(ty, "Vec")
}

/// Returns the inner type if `ty` matches `TypeName<T>`, otherwise `None`.
fn unwrap_type<'a>(ty: &'a syn::Type, type_name: &str) -> Option<&'a syn::Type> {
    let syn::Type::Path(type_path) = ungroup(ty) else {
        return None;
    };
    let seg = type_path.path.segments.last()?;
    let syn::PathArguments::AngleBracketed(args) = &seg.arguments else {
        return None;
    };

    if seg.ident == type_name
        && args.args.len() == 1
        && let syn::GenericArgument::Type(inner) = &args.args[0]
    {
        return Some(inner);
    }
    None
}

/// Unwrap `syn::Type::Group` nodes which may appear in macro-generated code.
///
/// When a macro captures a type with `$t:ty` and substitutes it, the type may be
/// wrapped in an invisible `Group` node. For example, `Option<String>` might appear
/// as `Group(Path("Option<String>"))` instead of just `Path("Option<String>")`.
///
/// Credit: serde_derive (https://github.com/serde-rs/serde)
fn ungroup(mut ty: &syn::Type) -> &syn::Type {
    while let syn::Type::Group(group) = ty {
        ty = &group.elem;
    }
    ty
}

/// Count the number of `Vec` wrappers in a type structure.
pub fn count_vec_depth(ts: &TypeStructure) -> usize {
    match ts {
        TypeStructure::Plain => 0,
        TypeStructure::Optional(inner) => count_vec_depth(inner),
        TypeStructure::Vector(inner) => 1 + count_vec_depth(inner),
    }
}

/// Scalars whose values can be objects or arrays in JSON.
///
/// These scalars represent structured data (not simple strings or numbers), so the macro
/// cannot validate Vec count — the Rust type is the user's responsibility.
const OBJECT_LIKE_SCALARS: &[&str] = &[
    "JSON",
    "MoveTypeLayout",
    "MoveTypeSignature",
    "OpenMoveTypeSignature",
];

/// Validate a parsed field path against the schema.
///
/// Checks that all fields in the path exist in the schema and that `[]` markers
/// match the schema's list types. List fields must always use `[]` explicitly.
///
/// Returns the terminal type name (the type of the last field in the path).
pub fn validate_path_against_schema<'a>(
    schema: &'a Schema,
    root_type: &'a str,
    path: &ParsedPath,
    span: proc_macro2::Span,
) -> Result<&'a str, syn::Error> {
    let mut current_type: &str = root_type;

    for segment in &path.segments {
        let field = schema
            .field(current_type, segment.field)
            .ok_or_else(|| field_not_found_error(schema, current_type, segment.field, span))?;

        if segment.is_list() && !field.is_list {
            return Err(syn::Error::new(
                span,
                format!(
                    "Cannot use '[]' on non-list field '{}' (type '{}')",
                    segment.field, field.type_name
                ),
            ));
        }

        if !segment.is_list() && field.is_list {
            return Err(syn::Error::new(
                span,
                format!(
                    "Field '{}' is a list type, use '{}[]' to iterate over it",
                    segment.field, segment.field
                ),
            ));
        }

        current_type = &field.type_name;
    }

    Ok(current_type)
}

/// Validate that a type name is a member of a union.
pub fn validate_union_member(
    schema: &Schema,
    union_type: &str,
    member_name: &str,
    span: proc_macro2::Span,
) -> Result<(), syn::Error> {
    let union_types = schema.union_types(union_type);
    if !union_types.contains(&member_name) {
        let suggestion = find_similar(&union_types, member_name);

        let mut msg = format!(
            "'{}' is not a member of union '{}'. Members: {}",
            member_name,
            union_type,
            union_types.join(", ")
        );
        if let Some(s) = suggestion {
            msg.push_str(&format!(". Did you mean '{}'?", s));
        }
        return Err(syn::Error::new(span, msg));
    }
    Ok(())
}

/// Returns true if the type name is a scalar that can represent objects or arrays.
pub fn is_object_like_scalar(type_name: &str) -> bool {
    OBJECT_LIKE_SCALARS.contains(&type_name)
}

/// Validate that the Rust type structure matches the `?` and `[]` markers in the path.
///
/// Walks segments and checks `TypeStructure` layers match:
/// - `?` markers on segments before the next `[]` → one `Optional` wrapper
/// - `[]` marker → one `Vector` wrapper
/// - `[]?` (elements_nullable) → one `Optional` wrapper on the element type
///
/// Multiple `?` markers between `[]` boundaries share one `Option` wrapper.
///
/// When `skip_vec_excess_check` is true, extra Vec wrappers beyond the list count are
/// allowed. This is used for object-like scalars (e.g., JSON) whose values can be arrays.
pub fn validate_type_matches_path(
    path: &ParsedPath<'_>,
    ty: &syn::Type,
    skip_vec_excess_check: bool,
) -> Result<(), syn::Error> {
    let analyzed = analyze_type(ty);
    let mut type_structure = &analyzed;

    let mut peeled_optional_in_group = false;

    for segment in &path.segments {
        // If segment has ?, peel Optional (first time in this group)
        if segment.is_nullable && !peeled_optional_in_group {
            let TypeStructure::Optional(inner) = type_structure else {
                return Err(syn::Error::new_spanned(
                    ty,
                    format!(
                        "'{}' is marked nullable with '?' but type is not wrapped in Option<...>",
                        segment.field
                    ),
                ));
            };
            type_structure = inner.as_ref();
            peeled_optional_in_group = true;
        }

        // If segment is a list, peel Vector (and handle []?)
        if let Some(list) = &segment.list {
            // Catch un-peeled Optional before peeling Vector
            if !peeled_optional_in_group && matches!(type_structure, TypeStructure::Optional(_)) {
                return Err(syn::Error::new_spanned(
                    ty,
                    format!(
                        "type is Option but no segment before '{}[]' has a '?' marker; \
                         add '?' to mark which segment is nullable",
                        segment.field
                    ),
                ));
            }

            // Peel Vector
            let TypeStructure::Vector(element_type) = type_structure else {
                return Err(syn::Error::new_spanned(
                    ty,
                    format!(
                        "field '{}' is a list but type has no Vec wrapper for it",
                        segment.field
                    ),
                ));
            };
            type_structure = element_type.as_ref();

            // Handle []? — peel Optional for element type
            if list.elements_nullable {
                let TypeStructure::Optional(inner) = type_structure else {
                    return Err(syn::Error::new_spanned(
                        ty,
                        format!(
                            "'{}' has '[]?' but element type is not wrapped in Option<...>",
                            segment.field
                        ),
                    ));
                };
                type_structure = inner.as_ref();
            }

            // New group starts after [].
            // If elements_nullable, keep peeled=true so subsequent `?` can coexist.
            peeled_optional_in_group = list.elements_nullable;
        }
    }

    // Final boundary: check for un-peeled Optional
    if !peeled_optional_in_group && matches!(type_structure, TypeStructure::Optional(_)) {
        let last_field = path.segments.last().map(|s| s.field).unwrap_or(path.raw);
        return Err(syn::Error::new_spanned(
            ty,
            format!(
                "type is Option but no '?' found at or before '{}'; \
                 add '?' to mark which segments are nullable",
                last_field
            ),
        ));
    }

    // Check for excess Vec wrappers
    if !skip_vec_excess_check && count_vec_depth(type_structure) > 0 {
        return Err(syn::Error::new_spanned(
            ty,
            format!(
                "type has {} excess Vec wrapper(s) but path '{}' has no matching list field(s)",
                count_vec_depth(type_structure),
                path.raw
            ),
        ));
    }

    Ok(())
}

/// Generate an error for a field not found, with "Did you mean?" suggestion.
fn field_not_found_error(
    schema: &Schema,
    type_name: &str,
    field_name: &str,
    span: proc_macro2::Span,
) -> syn::Error {
    let available = schema.field_names(type_name);
    let suggestion = find_similar(&available, field_name);

    let mut msg = format!("Field '{field_name}' not found on type '{type_name}'");

    if let Some(suggested) = suggestion {
        write!(msg, ". Did you mean '{suggested}'?").unwrap();
    } else if !available.is_empty() {
        // Sort for deterministic error messages (HashMap iteration order is random)
        let mut fields: Vec<_> = available;
        fields.sort();
        write!(msg, ". Available fields: {}", fields.join(", ")).unwrap();
    }

    syn::Error::new(span, msg)
}

/// Find a similar string using Levenshtein distance.
pub fn find_similar<'a>(candidates: &[&'a str], target: &str) -> Option<&'a str> {
    candidates
        .iter()
        .filter_map(|&candidate| {
            let distance = edit_distance::edit_distance(candidate, target);
            // Suggest if within 3 edits
            if distance <= 3 {
                Some((candidate, distance))
            } else {
                None
            }
        })
        .min_by_key(|(_, d)| *d)
        .map(|(c, _)| c)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_find_similar() {
        let candidates = vec!["address", "version", "digest", "owner"];
        assert_eq!(find_similar(&candidates, "addrss"), Some("address"));
        assert_eq!(find_similar(&candidates, "vesion"), Some("version"));
        assert_eq!(find_similar(&candidates, "xyz"), None);
    }
}