alef 0.67.2

//! Emits the swift-bridge mirror enum wrapper and its `From` conversion.
//!
//! Only unit variants are exposed in the bridge enum. Data variants are
//! absorbed by a catch-all `Unknown` variant when present.

use crate::backends::swift::gen_rust_crate::type_bridge::enum_from_string_fn_name;
use crate::codegen::generators::type_paths::resolve_type_path;
use crate::core::ir::EnumDef;
use std::collections::HashMap;

pub(crate) fn emit_enum_wrapper(en: &EnumDef, source_crate: &str, type_paths: &HashMap<String, String>) -> String {
    let mut out = String::new();
    let source_path = resolve_type_path(&en.name, source_crate, type_paths);

    out.push_str(&crate::backends::swift::template_env::render(
        "enum_unit_header.jinja",
        minijinja::context! {
            name => &en.name,
        },
    ));
    for variant in &en.variants {
        out.push_str(&crate::backends::swift::template_env::render(
            "enum_unit_variant.jinja",
            minijinja::context! {
                variant_name => &variant.name,
            },
        ));
    }

    out.push_str("}\n\n");

    out.push_str(&crate::backends::swift::template_env::render(
        "enum_from_impl_header.jinja",
        minijinja::context! {
            source_path => &source_path,
            name => &en.name,
        },
    ));
    out.push_str("        match val {\n");

    let has_cfg_variants = en.variants.iter().any(|v| v.cfg.is_some());

    for variant in &en.variants {
        let pattern = if variant.fields.is_empty() {
            variant.name.clone()
        } else if variant.is_tuple {
            format!("{}(..)", variant.name)
        } else {
            format!("{} {{ .. }}", variant.name)
        };

        // Mirror the dart enum_conversions emitter: variants gated by upstream `#[cfg(...)]`
        // (e.g. `Heif` under `#[cfg(feature = "heic")]`) must carry that same gate on the
        if let Some(condition) = variant.cfg.as_deref() {
            out.push_str("            #[cfg(");
            out.push_str(condition);
            out.push_str(")]\n");
        }

        out.push_str(&crate::backends::swift::template_env::render(
            "enum_from_variant.jinja",
            minijinja::context! {
                source_path => &source_path,
                variant_name => &variant.name,
                pattern => pattern,
            },
        ));
    }

    // 2. Any `variants` entry carries a `#[cfg(feature = "X")]` gate: when that feature
    // `#![allow(unreachable_patterns)]` at the crate root suppresses the redundant-arm
    if !en.excluded_variants.is_empty() || has_cfg_variants {
        out.push_str(&format!(
            "            _ => unreachable!(\"bridge enum variant of {} not exposed in binding\"),\n",
            en.name
        ));
    }

    out.push_str("        }\n");
    out.push_str("    }\n");
    out.push_str("}\n\n");

    let mut variants = String::new();
    for variant in &en.variants {
        let serde_name = serde_variant_wire_name(variant, en.serde_rename_all.as_deref());
        variants.push_str(&crate::backends::swift::template_env::render(
            "rust_enum_to_string_variant.rs.jinja",
            minijinja::context! {
                variant_name => &variant.name,
                serde_name => &serde_name,
            },
        ));
    }

    out.push_str(&crate::backends::swift::template_env::render(
        "rust_enum_to_string_impl.rs.jinja",
        minijinja::context! {
            enum_name => &en.name,
            variants => variants,
        },
    ));

    // `__alef_{enum}_from_swift_string` reconstructs an enum variant from the wire string
    // swift-bridge hands it, which only carries a variant's discriminant -- never its field
    // data. That is fine for a fieldless (unit) variant: `EnumName::Variant` is a complete
    // value. It is not possible for a variant with fields: there is no field data in a `&str`
    // to reconstruct with. Every call site that would invoke this helper already knows this
    // and only does so when `unit_enum_names` (all variants fieldless) contains the enum --
    // see `gen_rust_crate::shims` and `gen_rust_crate::wrappers::methods`. A tagged enum's
    // parameters are routed through `serde_json::from_str` instead, never through this
    // function. So when any variant carries fields, this helper has no caller and emitting it
    // is emitting dead code that also happens to be broken (a bare `EnumName::StructVariant`
    // or `EnumName::TupleVariant` path does not type-check, E0533/E0308). Skipping emission
    // entirely -- rather than patching the arms to compile and silently panic at runtime --
    // keeps the absence of a string-based reconstruction honest: the function simply does not
    // exist for enums it cannot serve. ~keep
    let is_unit_enum = en.variants.iter().all(|v| v.fields.is_empty());
    if is_unit_enum {
        let mut from_string_variants = String::new();
        for variant in &en.variants {
            let serde_name = serde_variant_wire_name(variant, en.serde_rename_all.as_deref());
            from_string_variants.push_str(&crate::backends::swift::template_env::render(
                "rust_enum_from_string_variant.rs.jinja",
                minijinja::context! {
                    variant_name => &variant.name,
                    serde_name => &serde_name,
                    source_path => &source_path,
                },
            ));
        }

        out.push_str(&crate::backends::swift::template_env::render(
            "rust_enum_from_string_impl.rs.jinja",
            minijinja::context! {
                fn_name => enum_from_string_fn_name(&en.name),
                enum_name => &en.name,
                source_path => &source_path,
                variants => from_string_variants,
            },
        ));
    }

    out
}

/// Compute the serde-serialized name for a unit enum variant.
///
/// Priority order:
/// 1. Explicit `#[serde(rename = "...")]` on the variant.
/// 2. `rename_all` transformation applied to the Rust identifier.
/// 3. Raw Rust identifier (no transformation).
fn serde_variant_wire_name(variant: &crate::core::ir::EnumVariant, rename_all: Option<&str>) -> String {
    crate::codegen::naming::wire_variant_value(&variant.name, variant.serde_rename.as_deref(), rename_all)
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::core::ir::{EnumDef, EnumVariant};

    fn make_unit_variant(name: &str, cfg: Option<&str>) -> EnumVariant {
        EnumVariant {
            name: name.to_string(),
            cfg: cfg.map(str::to_string),
            ..Default::default()
        }
    }

    fn make_tuple_variant(name: &str) -> EnumVariant {
        EnumVariant {
            name: name.to_string(),
            fields: vec![crate::core::ir::FieldDef {
                name: "0".to_string(),
                ty: crate::core::ir::TypeRef::String,
                ..Default::default()
            }],
            is_tuple: true,
            ..Default::default()
        }
    }

    fn make_struct_variant(name: &str) -> EnumVariant {
        EnumVariant {
            name: name.to_string(),
            fields: vec![crate::core::ir::FieldDef {
                name: "value".to_string(),
                ty: crate::core::ir::TypeRef::String,
                ..Default::default()
            }],
            is_tuple: false,
            ..Default::default()
        }
    }

    /// A fieldless enum is exactly what `__alef_{enum}_from_swift_string` can reconstruct
    /// from a wire string, and every call site that would invoke it only does so once
    /// `unit_enum_names` (all variants fieldless) contains the enum. The helper must still
    /// be emitted for this shape.
    #[test]
    fn fieldless_enum_still_emits_from_string_helper() {
        let en = EnumDef {
            name: "Mode".to_string(),
            variants: vec![make_unit_variant("Fast", None), make_unit_variant("Thorough", None)],
            methods: vec![],
            excluded_variants: vec![],
            ..Default::default()
        };
        let type_paths = std::collections::HashMap::new();
        let out = emit_enum_wrapper(&en, "mylib", &type_paths);
        assert!(
            out.contains("fn __alef_mode_from_swift_string"),
            "expected the from-string helper for a fieldless enum, got:\n{out}"
        );
        assert!(
            out.contains("\"Fast\" => mylib::Mode::Fast,"),
            "expected a bare unit-variant arm, got:\n{out}"
        );
    }

    /// A variant with fields cannot be reconstructed from a wire string alone -- there is no
    /// field data in a `&str`. Before this fix, `emit_enum_wrapper` still emitted a bare
    /// `EnumName::Variant` path for every variant regardless of fields, which does not
    /// type-check against a tuple or struct variant (E0308 / E0533). No call site ever
    /// invokes this helper for an enum with any fielded variant (they route through
    /// `serde_json::from_str` instead), so the correct fix is to not emit the helper at all
    /// for this shape, rather than patch the arms to compile and panic at runtime.
    #[test]
    fn fielded_enum_omits_from_string_helper_entirely() {
        let en = EnumDef {
            name: "AuthHeaderFormat".to_string(),
            variants: vec![make_unit_variant("None", None), make_tuple_variant("ApiKey")],
            methods: vec![],
            excluded_variants: vec![],
            ..Default::default()
        };
        let type_paths = std::collections::HashMap::new();
        let out = emit_enum_wrapper(&en, "mylib", &type_paths);
        assert!(
            !out.contains("__alef_auth_header_format_from_swift_string"),
            "expected no from-string helper for an enum with a tuple variant, got:\n{out}"
        );
        assert!(
            !out.contains("fn __alef_"),
            "expected no from-string helper of any name for an enum with a tuple variant, got:\n{out}"
        );
    }

    /// Same as above but for a struct variant (named fields), the other data-carrying shape.
    #[test]
    fn struct_variant_enum_omits_from_string_helper_entirely() {
        let en = EnumDef {
            name: "CacheBackend".to_string(),
            variants: vec![make_unit_variant("Memory", None), make_struct_variant("OpenDal")],
            methods: vec![],
            excluded_variants: vec![],
            ..Default::default()
        };
        let type_paths = std::collections::HashMap::new();
        let out = emit_enum_wrapper(&en, "mylib", &type_paths);
        assert!(
            !out.contains("fn __alef_"),
            "expected no from-string helper for an enum with a struct variant, got:\n{out}"
        );
    }

    /// When any variant in the primary list carries a `#[cfg(...)]` gate the
    /// From-impl match must emit a `_ => unreachable!()` catch-all arm so it
    /// remains exhaustive when that feature is inactive (E0004 guard).
    #[test]
    fn cfg_gated_variant_emits_catch_all_in_from_impl() {
        let en = EnumDef {
            name: "ImageOutputFormat".to_string(),
            variants: vec![
                make_unit_variant("Jpeg", None),
                make_unit_variant("Heif", Some(r#"feature = "heic""#)),
            ],
            methods: vec![],
            excluded_variants: vec![],
            ..Default::default()
        };
        let type_paths = std::collections::HashMap::new();
        let out = emit_enum_wrapper(&en, "mylib", &type_paths);
        assert!(
            out.contains("_ => unreachable!"),
            "expected catch-all `_ => unreachable!` arm when cfg-gated variant present, got:\n{out}"
        );
        assert!(
            out.contains("ImageOutputFormat"),
            "catch-all message must include the enum name, got:\n{out}"
        );
    }

    /// When no variant is cfg-gated and `excluded_variants` is empty, no catch-all
    /// should be emitted (the match is statically exhaustive without it).
    #[test]
    fn no_cfg_or_excluded_variants_does_not_emit_catch_all() {
        let en = EnumDef {
            name: "SimpleEnum".to_string(),
            variants: vec![make_unit_variant("A", None), make_unit_variant("B", None)],
            methods: vec![],
            excluded_variants: vec![],
            ..Default::default()
        };
        let type_paths = std::collections::HashMap::new();
        let out = emit_enum_wrapper(&en, "mylib", &type_paths);
        assert!(
            !out.contains("_ => unreachable!"),
            "unexpected catch-all arm in From impl for fully-covered enum:\n{out}"
        );
    }

    /// `excluded_variants` alone (no inline cfg gates) must still trigger the catch-all.
    #[test]
    fn excluded_variants_alone_emits_catch_all() {
        let en = EnumDef {
            name: "ImageOutputFormat".to_string(),
            variants: vec![make_unit_variant("Jpeg", None)],
            methods: vec![],
            excluded_variants: vec![make_unit_variant("ExcludedVariant", None)],
            ..Default::default()
        };
        let type_paths = std::collections::HashMap::new();
        let out = emit_enum_wrapper(&en, "mylib", &type_paths);
        assert!(
            out.contains("_ => unreachable!"),
            "expected catch-all arm when excluded_variants is non-empty, got:\n{out}"
        );
    }
}