//! Byte-equivalence between the Rust target and the JS rust.mjs baseline
//! against the AFI fixture. The downstream forcing function is the wire-
//! parity drivers under `tests/rust/`; this test catches divergence
//! earlier in the cycle without needing to spin a FastAPI fixture up.

use std::collections::BTreeMap;
use std::path::PathBuf;

use mizan_codegen::config::{Config, RustKernelSpec, SourceConfig};
use mizan_codegen::emit::{CodegenTarget, EmittedFile};
use mizan_codegen::emit::rust::RustCrate;
use mizan_codegen::fetch::parse_ir_from_str;


fn load_ir() -> mizan_codegen::ir::MizanIR {
    let path = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
        .join("tests/fixtures/afi_ir.kdl");
    parse_ir_from_str(&std::fs::read_to_string(&path).unwrap()).unwrap()
}


fn fixture_config() -> Config {
    Config {
        project_id: None,
        output: PathBuf::from("/tmp"),
        targets: vec!["rust".to_string()],
        source: SourceConfig { fastapi: None, django: None, rust: None, script: None },
        rust_kernel: Some(RustKernelSpec::Path {
            path: "../../../frontends/mizan-rust".to_string(),
        }),
        rust_crate_name: Some("fixture_client".to_string()),
    }
}


fn read_baseline(rel: &str) -> String {
    let path = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
        .join("tests/fixtures/baselines/rust")
        .join(rel);
    std::fs::read_to_string(&path)
        .unwrap_or_else(|e| panic!("read baseline {}: {e}", path.display()))
}


fn emit_index(files: &[EmittedFile]) -> BTreeMap<PathBuf, &str> {
    files.iter().map(|f| (f.rel_path.clone(), f.content.as_str())).collect()
}


fn assert_byte_equal(rel: &str, files: &BTreeMap<PathBuf, &str>) {
    let actual = files
        .get(&PathBuf::from(rel))
        .unwrap_or_else(|| panic!("Rust target did not produce {rel}"));
    let expected = read_baseline(rel);
    if *actual != expected {
        for (lineno, (a, b)) in actual.lines().zip(expected.lines()).enumerate() {
            if a != b {
                panic!(
                    "{rel} diverges at line {}:\n  expected: {b:?}\n  actual:   {a:?}",
                    lineno + 1,
                );
            }
        }
        panic!(
            "{rel} diverges in length: actual={} expected={}\n--- actual (last 200) ---\n{}\n--- expected (last 200) ---\n{}",
            actual.len(), expected.len(),
            &actual[actual.len().saturating_sub(200)..],
            &expected[expected.len().saturating_sub(200)..],
        );
    }
}


#[test]
fn rust_target_all_files_match_baseline() {
    let ir = load_ir();
    let files = RustCrate.emit(&ir, &fixture_config());
    let index = emit_index(&files);

    for rel in [
        "Cargo.toml",
        "src/lib.rs",
        "src/types.rs",
        "src/contexts/user.rs",
        "src/contexts/mod.rs",
        "src/functions/echo.rs",
        "src/functions/whoami.rs",
        "src/functions/find_user.rs",
        "src/functions/rename_user.rs",
        "src/functions/mod.rs",
        "src/mutations/update_profile.rs",
        "src/mutations/mod.rs",
    ] {
        assert_byte_equal(rel, &index);
    }
}
