alef-e2e 0.2.0

//! Go e2e test generator using testing.T.

use crate::config::E2eConfig;
use crate::escape::{go_string_literal, sanitize_filename};
use crate::field_access::FieldResolver;
use crate::fixture::{Assertion, Fixture, FixtureGroup};
use alef_core::backend::GeneratedFile;
use alef_core::config::AlefConfig;
use anyhow::Result;
use heck::ToUpperCamelCase;
use std::fmt::Write as FmtWrite;
use std::path::PathBuf;

use super::E2eCodegen;

/// Go e2e code generator.
pub struct GoCodegen;

impl E2eCodegen for GoCodegen {
    fn generate(
        &self,
        groups: &[FixtureGroup],
        e2e_config: &E2eConfig,
        _alef_config: &AlefConfig,
    ) -> Result<Vec<GeneratedFile>> {
        let lang = self.language_name();
        let output_base = PathBuf::from(&e2e_config.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 import_alias = overrides
            .and_then(|o| o.alias.as_ref())
            .cloned()
            .unwrap_or_else(|| "pkg".to_string());
        let result_var = &call.result_var;

        // Resolve package config.
        let go_pkg = e2e_config.packages.get("go");
        let go_module_path = go_pkg
            .and_then(|p| p.module.as_ref())
            .cloned()
            .unwrap_or_else(|| module_path.clone());
        let replace_path = go_pkg.and_then(|p| p.path.as_ref()).cloned();
        let go_version = go_pkg
            .and_then(|p| p.version.as_ref())
            .cloned()
            .unwrap_or_else(|| "v0.0.0".to_string());
        let field_resolver = FieldResolver::new(&e2e_config.fields, &e2e_config.fields_optional);

        // Generate go.mod.
        files.push(GeneratedFile {
            path: output_base.join("go.mod"),
            content: render_go_mod(&go_module_path, replace_path.as_deref(), &go_version),
            generated_header: false,
        });

        // Generate test files per category.
        for group in groups {
            let active: Vec<&Fixture> = group
                .fixtures
                .iter()
                .filter(|f| f.skip.as_ref().is_none_or(|s| !s.should_skip(lang)))
                .collect();

            if active.is_empty() {
                continue;
            }

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

        Ok(files)
    }

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

fn render_go_mod(go_module_path: &str, replace_path: Option<&str>, version: &str) -> String {
    let mut out = String::new();
    let _ = writeln!(out, "module e2e_go");
    let _ = writeln!(out);
    let _ = writeln!(out, "go 1.23");
    let _ = writeln!(out);
    let _ = writeln!(out, "require {go_module_path} {version}");

    if let Some(path) = replace_path {
        let _ = writeln!(out);
        let _ = writeln!(out, "replace {go_module_path} => {path}");
    }

    out
}

fn render_test_file(
    category: &str,
    fixtures: &[&Fixture],
    go_module_path: &str,
    import_alias: &str,
    function_name: &str,
    result_var: &str,
    args: &[crate::config::ArgMapping],
    field_resolver: &FieldResolver,
) -> String {
    let mut out = String::new();

    // Determine if we need the "strings" import.
    let needs_strings = fixtures.iter().any(|f| {
        f.assertions.iter().any(|a| {
            matches!(
                a.assertion_type.as_str(),
                "equals" | "contains" | "contains_all" | "not_contains" | "starts_with"
            )
        })
    });

    let _ = writeln!(out, "// E2e tests for category: {category}");
    let _ = writeln!(out, "package e2e_test");
    let _ = writeln!(out);
    let _ = writeln!(out, "import (");
    if needs_strings {
        let _ = writeln!(out, "\t\"strings\"");
    }
    let _ = writeln!(out, "\t\"testing\"");
    let _ = writeln!(out);
    let _ = writeln!(out, "\t{import_alias} \"{go_module_path}\"");
    let _ = writeln!(out, ")");
    let _ = writeln!(out);

    for (i, fixture) in fixtures.iter().enumerate() {
        render_test_function(
            &mut out,
            fixture,
            import_alias,
            function_name,
            result_var,
            args,
            field_resolver,
        );
        if i + 1 < fixtures.len() {
            let _ = writeln!(out);
        }
    }

    // Clean up trailing newlines.
    while out.ends_with("\n\n") {
        out.pop();
    }
    if !out.ends_with('\n') {
        out.push('\n');
    }
    out
}

fn render_test_function(
    out: &mut String,
    fixture: &Fixture,
    import_alias: &str,
    function_name: &str,
    result_var: &str,
    args: &[crate::config::ArgMapping],
    field_resolver: &FieldResolver,
) {
    let fn_name = fixture.id.to_upper_camel_case();
    let description = &fixture.description;

    let expects_error = fixture.assertions.iter().any(|a| a.assertion_type == "error");

    let args_str = build_args_string(&fixture.input, args);

    let _ = writeln!(out, "func Test_{fn_name}(t *testing.T) {{");
    let _ = writeln!(out, "\t// {description}");

    if expects_error {
        let _ = writeln!(out, "\t_, err := {import_alias}.{function_name}({args_str})");
        let _ = writeln!(out, "\tif err == nil {{");
        let _ = writeln!(out, "\t\tt.Errorf(\"expected an error, but call succeeded\")");
        let _ = writeln!(out, "\t}}");
        let _ = writeln!(out, "}}");
        return;
    }

    // Normal call: check for error assertions first.
    let _ = writeln!(out, "\t{result_var}, err := {import_alias}.{function_name}({args_str})");
    let _ = writeln!(out, "\tif err != nil {{");
    let _ = writeln!(out, "\t\tt.Fatalf(\"call failed: %v\", err)");
    let _ = writeln!(out, "\t}}");

    // Emit assertions.
    for assertion in &fixture.assertions {
        render_assertion(out, assertion, result_var, field_resolver);
    }

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

fn build_args_string(input: &serde_json::Value, args: &[crate::config::ArgMapping]) -> String {
    if args.is_empty() {
        return json_to_go(input);
    }

    let parts: Vec<String> = args
        .iter()
        .filter_map(|arg| {
            let val = input.get(&arg.field)?;
            if val.is_null() && arg.optional {
                return None;
            }
            Some(json_to_go(val))
        })
        .collect();

    parts.join(", ")
}

fn render_assertion(out: &mut String, assertion: &Assertion, result_var: &str, field_resolver: &FieldResolver) {
    let field_expr = match &assertion.field {
        Some(f) if !f.is_empty() => field_resolver.accessor(f, "go", result_var),
        _ => result_var.to_string(),
    };

    match assertion.assertion_type.as_str() {
        "equals" => {
            if let Some(expected) = &assertion.value {
                let go_val = json_to_go(expected);
                let _ = writeln!(out, "\tif strings.TrimSpace({field_expr}) != {go_val} {{");
                let _ = writeln!(out, "\t\tt.Errorf(\"equals mismatch: got %q\", {field_expr})");
                let _ = writeln!(out, "\t}}");
            }
        }
        "contains" => {
            if let Some(expected) = &assertion.value {
                let go_val = json_to_go(expected);
                let _ = writeln!(out, "\tif !strings.Contains({field_expr}, {go_val}) {{");
                let _ = writeln!(
                    out,
                    "\t\tt.Errorf(\"expected to contain %s, got %q\", {go_val}, {field_expr})"
                );
                let _ = writeln!(out, "\t}}");
            }
        }
        "contains_all" => {
            if let Some(values) = &assertion.values {
                for val in values {
                    let go_val = json_to_go(val);
                    let _ = writeln!(out, "\tif !strings.Contains({field_expr}, {go_val}) {{");
                    let _ = writeln!(out, "\t\tt.Errorf(\"expected to contain %s\", {go_val})");
                    let _ = writeln!(out, "\t}}");
                }
            }
        }
        "not_contains" => {
            if let Some(expected) = &assertion.value {
                let go_val = json_to_go(expected);
                let _ = writeln!(out, "\tif strings.Contains({field_expr}, {go_val}) {{");
                let _ = writeln!(
                    out,
                    "\t\tt.Errorf(\"expected NOT to contain %s, got %q\", {go_val}, {field_expr})"
                );
                let _ = writeln!(out, "\t}}");
            }
        }
        "not_empty" => {
            let _ = writeln!(out, "\tif len({field_expr}) == 0 {{");
            let _ = writeln!(out, "\t\tt.Errorf(\"expected non-empty value\")");
            let _ = writeln!(out, "\t}}");
        }
        "starts_with" => {
            if let Some(expected) = &assertion.value {
                let go_val = json_to_go(expected);
                let _ = writeln!(out, "\tif !strings.HasPrefix({field_expr}, {go_val}) {{");
                let _ = writeln!(
                    out,
                    "\t\tt.Errorf(\"expected to start with %s, got %q\", {go_val}, {field_expr})"
                );
                let _ = writeln!(out, "\t}}");
            }
        }
        "not_error" => {
            // Already handled by the `if err != nil` check above.
        }
        "error" => {
            // Handled at the test function level.
        }
        other => {
            let _ = writeln!(out, "\t// TODO: unsupported assertion type: {other}");
        }
    }
}

/// Convert a `serde_json::Value` to a Go literal string.
fn json_to_go(value: &serde_json::Value) -> String {
    match value {
        serde_json::Value::String(s) => go_string_literal(s),
        serde_json::Value::Bool(b) => b.to_string(),
        serde_json::Value::Number(n) => n.to_string(),
        serde_json::Value::Null => "nil".to_string(),
        // For complex types, serialize to JSON string and pass as literal.
        other => go_string_literal(&other.to_string()),
    }
}