alef_e2e/codegen/

zig.rs

//! Zig e2e test generator using std.testing.
//!
//! Generates `packages/zig/src/<crate>_test.zig` files from JSON fixtures,
//! driven entirely by `E2eConfig` and `CallConfig`.

use crate::config::E2eConfig;
use crate::escape::{escape_zig, sanitize_filename};
use crate::field_access::FieldResolver;
use crate::fixture::{Assertion, Fixture, FixtureGroup};
use alef_core::backend::GeneratedFile;
use alef_core::config::ResolvedCrateConfig;
use alef_core::hash::{self, CommentStyle};
use alef_core::template_versions::toolchain;
use anyhow::Result;
use heck::ToSnakeCase;
use std::collections::HashSet;
use std::fmt::Write as FmtWrite;
use std::path::PathBuf;

use super::E2eCodegen;
use super::client;

/// Zig e2e code generator.
pub struct ZigE2eCodegen;

impl E2eCodegen for ZigE2eCodegen {
    fn generate(
        &self,
        groups: &[FixtureGroup],
        e2e_config: &E2eConfig,
        config: &ResolvedCrateConfig,
    ) -> Result<Vec<GeneratedFile>> {
        let lang = self.language_name();
        let output_base = PathBuf::from(e2e_config.effective_output()).join(lang);

        let mut files = Vec::new();

        // Resolve call config with overrides.
        let call = &e2e_config.call;
        let overrides = call.overrides.get(lang);
        let _module_path = overrides
            .and_then(|o| o.module.as_ref())
            .cloned()
            .unwrap_or_else(|| call.module.clone());
        let function_name = overrides
            .and_then(|o| o.function.as_ref())
            .cloned()
            .unwrap_or_else(|| call.function.clone());
        let result_var = &call.result_var;

        // Resolve package config.
        let zig_pkg = e2e_config.resolve_package("zig");
        let pkg_path = zig_pkg
            .as_ref()
            .and_then(|p| p.path.as_ref())
            .cloned()
            .unwrap_or_else(|| "../../packages/zig".to_string());
        let pkg_name = zig_pkg
            .as_ref()
            .and_then(|p| p.name.as_ref())
            .cloned()
            .unwrap_or_else(|| config.name.to_snake_case());

        // Generate build.zig.zon (Zig package manifest).
        files.push(GeneratedFile {
            path: output_base.join("build.zig.zon"),
            content: render_build_zig_zon(&pkg_name, &pkg_path, e2e_config.dep_mode),
            generated_header: false,
        });

        // Get the module name for imports.
        let module_name = config.zig_module_name();

        // Generate build.zig - collect test file names first.
        let field_resolver = FieldResolver::new(
            &e2e_config.fields,
            &e2e_config.fields_optional,
            &e2e_config.result_fields,
            &e2e_config.fields_array,
            &e2e_config.fields_method_calls,
        );

        // Generate test files per category and collect their names.
        let mut test_filenames: Vec<String> = Vec::new();
        for group in groups {
            let active: Vec<&Fixture> = group
                .fixtures
                .iter()
                .filter(|f| super::should_include_fixture(f, lang, e2e_config))
                .collect();

            if active.is_empty() {
                continue;
            }

            let filename = format!("{}_test.zig", sanitize_filename(&group.category));
            test_filenames.push(filename.clone());
            let content = render_test_file(
                &group.category,
                &active,
                e2e_config,
                &function_name,
                result_var,
                &e2e_config.call.args,
                &field_resolver,
                &e2e_config.fields_enum,
                &module_name,
            );
            files.push(GeneratedFile {
                path: output_base.join("src").join(filename),
                content,
                generated_header: true,
            });
        }

        // Generate build.zig with collected test files.
        files.insert(
            files
                .iter()
                .position(|f| f.path.file_name().is_some_and(|n| n == "build.zig.zon"))
                .unwrap_or(1),
            GeneratedFile {
                path: output_base.join("build.zig"),
                content: render_build_zig(&test_filenames),
                generated_header: false,
            },
        );

        Ok(files)
    }

    fn language_name(&self) -> &'static str {
        "zig"
    }
}

// ---------------------------------------------------------------------------
// Rendering
// ---------------------------------------------------------------------------

fn render_build_zig_zon(pkg_name: &str, pkg_path: &str, dep_mode: crate::config::DependencyMode) -> String {
    let dep_block = match dep_mode {
        crate::config::DependencyMode::Registry => {
            // For registry mode, use a dummy hash (in real Zig, hash must be computed).
            format!(
                r#".{{
            .url = "https://registry.example.com/{pkg_name}/v0.1.0.tar.gz",
            .hash = "0000000000000000000000000000000000000000000000000000000000000000",
        }}"#
            )
        }
        crate::config::DependencyMode::Local => {
            format!(r#".{{ .path = "{pkg_path}" }}"#)
        }
    };

    let min_zig = toolchain::MIN_ZIG_VERSION;
    // Zig 0.16+ requires a fingerprint of the form (crc32_ieee(name) << 32) | id.
    let name_bytes: &[u8] = b"e2e_zig";
    let mut crc: u32 = 0xffff_ffff;
    for byte in name_bytes {
        crc ^= *byte as u32;
        for _ in 0..8 {
            let mask = (crc & 1).wrapping_neg();
            crc = (crc >> 1) ^ (0xedb8_8320 & mask);
        }
    }
    let name_crc: u32 = !crc;
    let mut id: u32 = 0x811c_9dc5;
    for byte in name_bytes {
        id ^= *byte as u32;
        id = id.wrapping_mul(0x0100_0193);
    }
    if id == 0 || id == 0xffff_ffff {
        id = 0x1;
    }
    let fingerprint: u64 = ((name_crc as u64) << 32) | (id as u64);
    format!(
        r#".{{
    .name = .e2e_zig,
    .version = "0.1.0",
    .fingerprint = 0x{fingerprint:016x},
    .minimum_zig_version = "{min_zig}",
    .dependencies = .{{
        .{pkg_name} = {dep_block},
    }},
    .paths = .{{
        "build.zig",
        "build.zig.zon",
        "src",
    }},
}}
"#
    )
}

fn render_build_zig(test_filenames: &[String]) -> String {
    if test_filenames.is_empty() {
        return r#"const std = @import("std");

pub fn build(b: *std.Build) void {
    const target = b.standardTargetOptions(.{});
    const optimize = b.standardOptimizeOption(.{});

    const test_step = b.step("test", "Run tests");
}
"#
        .to_string();
    }

    let mut content = String::from("const std = @import(\"std\");\n\npub fn build(b: *std.Build) void {\n");
    content.push_str("    const target = b.standardTargetOptions(.{});\n");
    content.push_str("    const optimize = b.standardOptimizeOption(.{});\n");
    content.push_str("    const test_step = b.step(\"test\", \"Run tests\");\n");
    content.push_str("    const ffi_path = b.option([]const u8, \"ffi_path\", \"Path to directory containing libkreuzberg_ffi\") orelse \"../../target/debug\";\n");
    content.push_str("    const ffi_include = b.option([]const u8, \"ffi_include_path\", \"Path to directory containing kreuzberg FFI header\") orelse \"../../crates/kreuzberg-ffi/include\";\n\n");
    content.push_str("    const kreuzberg_module = b.addModule(\"kreuzberg\", .{\n");
    content.push_str("        .root_source_file = b.path(\"../../packages/zig/src/kreuzberg.zig\"),\n");
    content.push_str("        .target = target,\n");
    content.push_str("        .optimize = optimize,\n");
    content.push_str("    });\n");
    content.push_str("    kreuzberg_module.addLibraryPath(.{ .cwd_relative = ffi_path });\n");
    content.push_str("    kreuzberg_module.addIncludePath(.{ .cwd_relative = ffi_include });\n");
    content.push_str("    kreuzberg_module.linkSystemLibrary(\"kreuzberg_ffi\", .{});\n\n");

    for filename in test_filenames {
        // Convert filename like "basic_test.zig" to a test name
        let test_name = filename.trim_end_matches("_test.zig");
        content.push_str(&format!("    const {test_name}_module = b.createModule(.{{\n"));
        content.push_str(&format!("        .root_source_file = b.path(\"src/{filename}\"),\n"));
        content.push_str("        .target = target,\n");
        content.push_str("        .optimize = optimize,\n");
        content.push_str("    });\n");
        content.push_str(&format!(
            "    {test_name}_module.addImport(\"kreuzberg\", kreuzberg_module);\n"
        ));
        content.push_str(&format!("    const {test_name}_tests = b.addTest(.{{\n"));
        content.push_str(&format!("        .root_module = {test_name}_module,\n"));
        content.push_str("    });\n");
        content.push_str(&format!(
            "    const {test_name}_run = b.addRunArtifact({test_name}_tests);\n"
        ));
        content.push_str(&format!("    test_step.dependOn(&{test_name}_run.step);\n\n"));
    }

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

// ---------------------------------------------------------------------------
// HTTP server test rendering — shared-driver integration
// ---------------------------------------------------------------------------

/// Renderer that emits Zig `test "..." { ... }` blocks targeting a mock server
/// via `std.http.Client`. Satisfies [`client::TestClientRenderer`] so the shared
/// [`client::http_call::render_http_test`] driver drives the call sequence.
struct ZigTestClientRenderer;

impl client::TestClientRenderer for ZigTestClientRenderer {
    fn language_name(&self) -> &'static str {
        "zig"
    }

    fn render_test_open(&self, out: &mut String, fn_name: &str, description: &str, skip_reason: Option<&str>) {
        if let Some(reason) = skip_reason {
            let _ = writeln!(out, "test \"{fn_name}\" {{");
            let _ = writeln!(out, "    // {description}");
            let _ = writeln!(out, "    // skipped: {reason}");
            let _ = writeln!(out, "    return error.SkipZigTest;");
        } else {
            let _ = writeln!(out, "test \"{fn_name}\" {{");
            let _ = writeln!(out, "    // {description}");
        }
    }

    fn render_test_close(&self, out: &mut String) {
        let _ = writeln!(out, "}}");
    }

    fn render_call(&self, out: &mut String, ctx: &client::CallCtx<'_>) {
        let method = ctx.method.to_uppercase();
        let fixture_id = ctx.path.trim_start_matches("/fixtures/");

        let _ = writeln!(out, "    var gpa: std.heap.DebugAllocator(.{{}}) = .init;");
        let _ = writeln!(out, "    defer _ = gpa.deinit();");
        let _ = writeln!(out, "    const allocator = gpa.allocator();");

        let _ = writeln!(out, "    var url_buf: [512]u8 = undefined;");
        let _ = writeln!(
            out,
            "    const url = try std.fmt.bufPrint(&url_buf, \"{{s}}/fixtures/{fixture_id}\", .{{std.posix.getenv(\"MOCK_SERVER_URL\") orelse \"http://localhost:8080\"}});"
        );

        // Headers
        if !ctx.headers.is_empty() {
            let mut header_pairs: Vec<(&String, &String)> = ctx.headers.iter().collect();
            header_pairs.sort_by_key(|(k, _)| k.as_str());
            let _ = writeln!(out, "    const headers = [_]std.http.Header{{");
            for (k, v) in &header_pairs {
                let ek = escape_zig(k);
                let ev = escape_zig(v);
                let _ = writeln!(out, "        .{{ .name = \"{ek}\", .value = \"{ev}\" }},");
            }
            let _ = writeln!(out, "    }};");
        }

        // Body
        if let Some(body) = ctx.body {
            let json_str = serde_json::to_string(body).unwrap_or_default();
            let escaped = escape_zig(&json_str);
            let _ = writeln!(out, "    const body_bytes: []const u8 = \"{escaped}\";");
        }

        let headers_arg = if ctx.headers.is_empty() { "&.{}" } else { "&headers" };
        let has_body = ctx.body.is_some();

        let _ = writeln!(
            out,
            "    var http_client = std.http.Client{{ .allocator = allocator }};"
        );
        let _ = writeln!(out, "    defer http_client.deinit();");
        let _ = writeln!(out, "    var response_body = std.ArrayList(u8).init(allocator);");
        let _ = writeln!(out, "    defer response_body.deinit();");

        let method_zig = match method.as_str() {
            "GET" => ".GET",
            "POST" => ".POST",
            "PUT" => ".PUT",
            "DELETE" => ".DELETE",
            "PATCH" => ".PATCH",
            "HEAD" => ".HEAD",
            "OPTIONS" => ".OPTIONS",
            _ => ".GET",
        };

        let payload_field = if has_body { ", .payload = body_bytes" } else { "" };
        let _ = writeln!(
            out,
            "    const {rv} = try http_client.fetch(.{{ .location = .{{ .url = url }}, .method = {method_zig}, .extra_headers = {headers_arg}{payload_field}, .response_storage = .{{ .dynamic = &response_body }} }});",
            rv = ctx.response_var,
        );
    }

    fn render_assert_status(&self, out: &mut String, response_var: &str, status: u16) {
        let _ = writeln!(
            out,
            "    try testing.expectEqual(@as(u10, {status}), @intFromEnum({response_var}.status));"
        );
    }

    fn render_assert_header(&self, out: &mut String, _response_var: &str, name: &str, expected: &str) {
        let ename = escape_zig(&name.to_lowercase());
        match expected {
            "<<present>>" => {
                let _ = writeln!(
                    out,
                    "    // assert header '{ename}' is present (header inspection not yet implemented)"
                );
            }
            "<<absent>>" => {
                let _ = writeln!(
                    out,
                    "    // assert header '{ename}' is absent (header inspection not yet implemented)"
                );
            }
            "<<uuid>>" => {
                let _ = writeln!(
                    out,
                    "    // assert header '{ename}' matches UUID pattern (header inspection not yet implemented)"
                );
            }
            exact => {
                let evalue = escape_zig(exact);
                let _ = writeln!(
                    out,
                    "    // assert header '{ename}' == \"{evalue}\" (header inspection not yet implemented)"
                );
            }
        }
    }

    fn render_assert_json_body(&self, out: &mut String, _response_var: &str, expected: &serde_json::Value) {
        let json_str = serde_json::to_string(expected).unwrap_or_default();
        let escaped = escape_zig(&json_str);
        let _ = writeln!(
            out,
            "    try testing.expectEqualStrings(\"{escaped}\", response_body.items);"
        );
    }

    fn render_assert_partial_body(&self, out: &mut String, _response_var: &str, expected: &serde_json::Value) {
        if let Some(obj) = expected.as_object() {
            for (key, val) in obj {
                let ekey = escape_zig(key);
                let eval = escape_zig(&serde_json::to_string(val).unwrap_or_default());
                let _ = writeln!(
                    out,
                    "    // assert body contains field \"{ekey}\" = \"{eval}\" (partial JSON not yet implemented)"
                );
            }
        }
    }

    fn render_assert_validation_errors(
        &self,
        out: &mut String,
        _response_var: &str,
        errors: &[crate::fixture::ValidationErrorExpectation],
    ) {
        for ve in errors {
            let loc = ve.loc.join(".");
            let escaped_loc = escape_zig(&loc);
            let escaped_msg = escape_zig(&ve.msg);
            let _ = writeln!(
                out,
                "    // assert validation error at \"{escaped_loc}\": \"{escaped_msg}\" (not yet implemented)"
            );
        }
    }
}

/// Render a Zig `test "..." { ... }` block for an HTTP server fixture.
///
/// Delegates to the shared [`client::http_call::render_http_test`] driver via
/// [`ZigTestClientRenderer`].
fn render_http_test_case(out: &mut String, fixture: &Fixture) {
    client::http_call::render_http_test(out, &ZigTestClientRenderer, fixture);
}

// ---------------------------------------------------------------------------
// Function-call test rendering
// ---------------------------------------------------------------------------

#[allow(clippy::too_many_arguments)]
fn render_test_file(
    category: &str,
    fixtures: &[&Fixture],
    e2e_config: &E2eConfig,
    function_name: &str,
    result_var: &str,
    args: &[crate::config::ArgMapping],
    field_resolver: &FieldResolver,
    enum_fields: &HashSet<String>,
    module_name: &str,
) -> String {
    let mut out = String::new();
    out.push_str(&hash::header(CommentStyle::DoubleSlash));
    let _ = writeln!(out, "const std = @import(\"std\");");
    let _ = writeln!(out, "const testing = std.testing;");
    let _ = writeln!(out, "const {module_name} = @import(\"{module_name}\");");
    let _ = writeln!(out);

    let _ = writeln!(out, "// E2e tests for category: {category}");
    let _ = writeln!(out);

    for fixture in fixtures {
        if fixture.http.is_some() {
            render_http_test_case(&mut out, fixture);
        } else {
            render_test_fn(
                &mut out,
                fixture,
                e2e_config,
                function_name,
                result_var,
                args,
                field_resolver,
                enum_fields,
                module_name,
            );
        }
        let _ = writeln!(out);
    }

    out
}

#[allow(clippy::too_many_arguments)]
fn render_test_fn(
    out: &mut String,
    fixture: &Fixture,
    e2e_config: &E2eConfig,
    _function_name: &str,
    _result_var: &str,
    _args: &[crate::config::ArgMapping],
    field_resolver: &FieldResolver,
    enum_fields: &HashSet<String>,
    module_name: &str,
) {
    // Resolve per-fixture call config.
    let call_config = e2e_config.resolve_call(fixture.call.as_deref());
    let lang = "zig";
    let call_overrides = call_config.overrides.get(lang);
    let function_name = call_overrides
        .and_then(|o| o.function.as_ref())
        .cloned()
        .unwrap_or_else(|| call_config.function.clone());
    let result_var = &call_config.result_var;
    let args = &call_config.args;
    let is_async = call_overrides.and_then(|o| o.r#async).unwrap_or(call_config.r#async);

    let test_name = fixture.id.to_snake_case();
    let description = &fixture.description;
    let expects_error = fixture.assertions.iter().any(|a| a.assertion_type == "error");

    let (setup_lines, args_str) = build_args_and_setup(&fixture.input, args, &fixture.id, module_name);

    let _ = writeln!(out, "test \"{test_name}\" {{");
    let _ = writeln!(out, "    // {description}");

    // Only emit allocator setup when setup lines actually need it (avoids unused-variable errors).
    let needs_alloc = !setup_lines.is_empty();
    if needs_alloc {
        let _ = writeln!(out, "    var gpa: std.heap.DebugAllocator(.{{}}) = .init;");
        let _ = writeln!(out, "    defer _ = gpa.deinit();");
        let _ = writeln!(out, "    const allocator = gpa.allocator();");
        let _ = writeln!(out);
    }

    for line in &setup_lines {
        let _ = writeln!(out, "    {line}");
    }

    if expects_error {
        // Error-path test: use error union syntax `!T` and try-catch.
        if is_async {
            let _ = writeln!(
                out,
                "    // Note: async functions not yet fully supported; treating as sync"
            );
        }
        let _ = writeln!(
            out,
            "    const result = {module_name}.{function_name}({args_str}) catch {{"
        );
        let _ = writeln!(out, "        try testing.expect(true); // Error occurred as expected");
        let _ = writeln!(out, "        return;");
        let _ = writeln!(out, "    }};");
        // Whether any non-error assertion will emit code that references `result`.
        // If not, we must explicitly discard `result` to satisfy Zig's
        // strict-unused-locals rule.
        let any_emits_code = fixture
            .assertions
            .iter()
            .filter(|a| a.assertion_type != "error")
            .any(|a| assertion_emits_code(a, field_resolver));
        if any_emits_code {
            let _ = writeln!(out, "    // Perform success assertions if any");
            for assertion in &fixture.assertions {
                if assertion.assertion_type != "error" {
                    render_assertion(out, assertion, result_var, field_resolver, enum_fields);
                }
            }
        } else {
            let _ = writeln!(out, "    _ = result;");
        }
    } else if fixture.assertions.is_empty() {
        // No assertions: emit a call to verify compilation.
        if is_async {
            let _ = writeln!(
                out,
                "    // Note: async functions not yet fully supported; treating as sync"
            );
        }
        let _ = writeln!(out, "    _ = try {module_name}.{function_name}({args_str});");
    } else {
        // Happy path: call and assert. Detect whether any assertion actually
        // emits code that references `result` (some — like `not_error` — emit
        // nothing) so we don't leave an unused local, which Zig 0.16 rejects.
        if is_async {
            let _ = writeln!(
                out,
                "    // Note: async functions not yet fully supported; treating as sync"
            );
        }
        let any_emits_code = fixture
            .assertions
            .iter()
            .any(|a| assertion_emits_code(a, field_resolver));
        if any_emits_code {
            let _ = writeln!(
                out,
                "    const {result_var} = try {module_name}.{function_name}({args_str});"
            );
            for assertion in &fixture.assertions {
                render_assertion(out, assertion, result_var, field_resolver, enum_fields);
            }
        } else {
            let _ = writeln!(out, "    _ = try {module_name}.{function_name}({args_str});");
        }
    }

    let _ = writeln!(out, "}}");
}

/// Predicate matching `render_assertion`: returns true when the assertion
/// would emit at least one statement that references the result variable.
fn assertion_emits_code(assertion: &Assertion, field_resolver: &FieldResolver) -> bool {
    if let Some(f) = &assertion.field {
        if !f.is_empty() && !field_resolver.is_valid_for_result(f) {
            return false;
        }
    }
    matches!(
        assertion.assertion_type.as_str(),
        "equals"
            | "contains"
            | "contains_all"
            | "not_contains"
            | "not_empty"
            | "is_empty"
            | "starts_with"
            | "ends_with"
            | "min_length"
            | "max_length"
            | "count_min"
            | "count_equals"
            | "is_true"
            | "is_false"
            | "greater_than"
            | "less_than"
            | "greater_than_or_equal"
            | "less_than_or_equal"
            | "contains_any"
    )
}

/// Build setup lines and the argument list for the function call.
fn build_args_and_setup(
    input: &serde_json::Value,
    args: &[crate::config::ArgMapping],
    fixture_id: &str,
    _module_name: &str,
) -> (Vec<String>, String) {
    if args.is_empty() {
        return (Vec::new(), String::new());
    }

    let mut setup_lines: Vec<String> = Vec::new();
    let mut parts: Vec<String> = Vec::new();

    for arg in args {
        if arg.arg_type == "mock_url" {
            setup_lines.push(format!(
                "var {} = try allocator.alloc(u8, std.fmt.bufPrint(undefined, \"{{s}}/fixtures/{fixture_id}\", .{{std.posix.getenv(\"MOCK_SERVER_URL\") orelse \"http://localhost:8080\"}}) catch 0)",
                arg.name,
            ));
            parts.push(arg.name.clone());
            continue;
        }

        // The Zig wrapper accepts struct parameters (e.g. `ExtractionConfig`)
        // as JSON `[]const u8`, converting them to opaque FFI handles via the
        // `<prefix>_<snake>_from_json` helper at the binding layer. Emit the
        // fixture's configuration value as a JSON string literal, falling back
        // to `"{}"` when the fixture omits a config so callers exercise the
        // default path.
        if arg.name == "config" && arg.arg_type == "json_object" {
            let field = arg.field.strip_prefix("input.").unwrap_or(&arg.field);
            let json_str = match input.get(field) {
                Some(serde_json::Value::Null) | None => "{}".to_string(),
                Some(v) => serde_json::to_string(v).unwrap_or_else(|_| "{}".to_string()),
            };
            parts.push(format!("\"{}\"", escape_zig(&json_str)));
            continue;
        }

        let field = arg.field.strip_prefix("input.").unwrap_or(&arg.field);
        let val = input.get(field);
        match val {
            None | Some(serde_json::Value::Null) if arg.optional => {
                // Zig functions don't have default arguments, so we must
                // pass `null` explicitly for every optional parameter.
                parts.push("null".to_string());
            }
            None | Some(serde_json::Value::Null) => {
                let default_val = match arg.arg_type.as_str() {
                    "string" => "\"\"".to_string(),
                    "int" | "integer" => "0".to_string(),
                    "float" | "number" => "0.0".to_string(),
                    "bool" | "boolean" => "false".to_string(),
                    "json_object" => "\"{}\"".to_string(),
                    _ => "null".to_string(),
                };
                parts.push(default_val);
            }
            Some(v) => {
                // For `json_object` arguments other than `config` (handled
                // above) the Zig binding accepts a JSON `[]const u8`, so we
                // serialize the entire fixture value as a single JSON string
                // literal rather than rendering it as a Zig array/struct.
                if arg.arg_type == "json_object" {
                    let json_str = serde_json::to_string(v).unwrap_or_default();
                    parts.push(format!("\"{}\"", escape_zig(&json_str)));
                } else {
                    parts.push(json_to_zig(v));
                }
            }
        }
    }

    (setup_lines, parts.join(", "))
}

fn render_assertion(
    out: &mut String,
    assertion: &Assertion,
    result_var: &str,
    field_resolver: &FieldResolver,
    enum_fields: &HashSet<String>,
) {
    // Skip assertions on fields that don't exist on the result type.
    if let Some(f) = &assertion.field {
        if !f.is_empty() && !field_resolver.is_valid_for_result(f) {
            let _ = writeln!(out, "    // skipped: field '{{f}}' not available on result type");
            return;
        }
    }

    // Determine if this field is an enum type.
    let _field_is_enum = assertion
        .field
        .as_deref()
        .is_some_and(|f| enum_fields.contains(f) || enum_fields.contains(field_resolver.resolve(f)));

    let field_expr = match &assertion.field {
        Some(f) if !f.is_empty() => field_resolver.accessor(f, "zig", result_var),
        _ => result_var.to_string(),
    };

    match assertion.assertion_type.as_str() {
        "equals" => {
            if let Some(expected) = &assertion.value {
                let zig_val = json_to_zig(expected);
                let _ = writeln!(out, "    try testing.expectEqual({zig_val}, {field_expr});");
            }
        }
        "contains" => {
            if let Some(expected) = &assertion.value {
                let zig_val = json_to_zig(expected);
                let _ = writeln!(
                    out,
                    "    try testing.expect(std.mem.indexOf(u8, {field_expr}, {zig_val}) != null);"
                );
            }
        }
        "contains_all" => {
            if let Some(values) = &assertion.values {
                for val in values {
                    let zig_val = json_to_zig(val);
                    let _ = writeln!(
                        out,
                        "    try testing.expect(std.mem.indexOf(u8, {field_expr}, {zig_val}) != null);"
                    );
                }
            }
        }
        "not_contains" => {
            if let Some(expected) = &assertion.value {
                let zig_val = json_to_zig(expected);
                let _ = writeln!(
                    out,
                    "    try testing.expect(std.mem.indexOf(u8, {field_expr}, {zig_val}) == null);"
                );
            }
        }
        "not_empty" => {
            let _ = writeln!(out, "    try testing.expect({field_expr}.len > 0);");
        }
        "is_empty" => {
            let _ = writeln!(out, "    try testing.expect({field_expr}.len == 0);");
        }
        "starts_with" => {
            if let Some(expected) = &assertion.value {
                let zig_val = json_to_zig(expected);
                let _ = writeln!(
                    out,
                    "    try testing.expect(std.mem.startsWith(u8, {field_expr}, {zig_val}));"
                );
            }
        }
        "ends_with" => {
            if let Some(expected) = &assertion.value {
                let zig_val = json_to_zig(expected);
                let _ = writeln!(
                    out,
                    "    try testing.expect(std.mem.endsWith(u8, {field_expr}, {zig_val}));"
                );
            }
        }
        "min_length" => {
            if let Some(val) = &assertion.value {
                if let Some(n) = val.as_u64() {
                    let _ = writeln!(out, "    try testing.expect({field_expr}.len >= {n});");
                }
            }
        }
        "max_length" => {
            if let Some(val) = &assertion.value {
                if let Some(n) = val.as_u64() {
                    let _ = writeln!(out, "    try testing.expect({field_expr}.len <= {n});");
                }
            }
        }
        "count_min" => {
            if let Some(val) = &assertion.value {
                if let Some(n) = val.as_u64() {
                    let _ = writeln!(out, "    try testing.expect({field_expr}.len >= {n});");
                }
            }
        }
        "count_equals" => {
            if let Some(val) = &assertion.value {
                if let Some(n) = val.as_u64() {
                    let _ = writeln!(out, "    try testing.expectEqual({n}, {field_expr}.len);");
                }
            }
        }
        "is_true" => {
            let _ = writeln!(out, "    try testing.expect({field_expr});");
        }
        "is_false" => {
            let _ = writeln!(out, "    try testing.expect(!{field_expr});");
        }
        "not_error" => {
            // Already handled by the call succeeding.
        }
        "error" => {
            // Handled at the test function level.
        }
        "greater_than" => {
            if let Some(val) = &assertion.value {
                let zig_val = json_to_zig(val);
                let _ = writeln!(out, "    try testing.expect({field_expr} > {zig_val});");
            }
        }
        "less_than" => {
            if let Some(val) = &assertion.value {
                let zig_val = json_to_zig(val);
                let _ = writeln!(out, "    try testing.expect({field_expr} < {zig_val});");
            }
        }
        "greater_than_or_equal" => {
            if let Some(val) = &assertion.value {
                let zig_val = json_to_zig(val);
                let _ = writeln!(out, "    try testing.expect({field_expr} >= {zig_val});");
            }
        }
        "less_than_or_equal" => {
            if let Some(val) = &assertion.value {
                let zig_val = json_to_zig(val);
                let _ = writeln!(out, "    try testing.expect({field_expr} <= {zig_val});");
            }
        }
        "contains_any" => {
            if let Some(values) = &assertion.values {
                for val in values {
                    let zig_val = json_to_zig(val);
                    let _ = writeln!(
                        out,
                        "    try testing.expect(std.mem.indexOf(u8, {field_expr}, {zig_val}) != null);"
                    );
                }
            }
        }
        "matches_regex" => {
            let _ = writeln!(out, "    // regex match not yet implemented for Zig");
        }
        "method_result" => {
            let _ = writeln!(out, "    // method_result assertions not yet implemented for Zig");
        }
        other => {
            panic!("Zig e2e generator: unsupported assertion type: {other}");
        }
    }
}

/// Convert a `serde_json::Value` to a Zig literal string.
fn json_to_zig(value: &serde_json::Value) -> String {
    match value {
        serde_json::Value::String(s) => format!("\"{}\"", escape_zig(s)),
        serde_json::Value::Bool(b) => b.to_string(),
        serde_json::Value::Number(n) => n.to_string(),
        serde_json::Value::Null => "null".to_string(),
        serde_json::Value::Array(arr) => {
            let items: Vec<String> = arr.iter().map(json_to_zig).collect();
            format!("&.{{{}}}", items.join(", "))
        }
        serde_json::Value::Object(_) => {
            let json_str = serde_json::to_string(value).unwrap_or_default();
            format!("\"{}\"", escape_zig(&json_str))
        }
    }
}