//! A number read through serde_json must be the number written (improvise-6yvg,
//! improvise-dz8c). The rule and its derivation: `context/code/protocol.md`.

use serde_json::Value;

/// Every NORMAL serde_json dependency in the workspace, and those lacking
/// `float_roundtrip`, each spelled `package (target)`.
fn lossy_json_dependencies(metadata: &Value) -> (Vec<String>, Vec<String>) {
    let mut checked = vec![];
    let mut lossy = vec![];
    let packages = metadata["packages"]
        .as_array()
        .expect("metadata lists packages");
    for package in packages {
        let name = package["name"].as_str().expect("a package has a name");
        let deps = package["dependencies"]
            .as_array()
            .expect("a package lists deps");
        for dep in deps {
            if dep["name"] != "serde_json" || !dep["kind"].is_null() {
                continue;
            }
            let target = dep["target"].as_str().unwrap_or("all targets");
            let spelled = format!("{name} ({target})");
            let features = dep["features"].as_array().expect("a dep lists features");
            if !features.iter().any(|f| f == "float_roundtrip") {
                lossy.push(spelled.clone());
            }
            checked.push(spelled);
        }
    }
    (checked, lossy)
}

/// Derived from `cargo metadata`, not listed: a new crate that can parse JSON
/// is covered the day it declares the dependency. Evidence file.
#[test]
fn every_crate_that_can_parse_json_enables_float_roundtrip() {
    let out = std::process::Command::new(env!("CARGO"))
        .current_dir(env!("CARGO_MANIFEST_DIR"))
        .args(["metadata", "--no-deps", "--format-version", "1"])
        .output()
        .expect("cargo metadata must run");
    assert!(
        out.status.success(),
        "cargo metadata failed: {}",
        String::from_utf8_lossy(&out.stderr)
    );
    let metadata: Value = serde_json::from_slice(&out.stdout).expect("metadata is JSON");
    let (checked, lossy) = lossy_json_dependencies(&metadata);
    assert!(
        checked.len() >= 2,
        "the derivation found {checked:?}: too few to be reading the metadata right"
    );
    assert!(
        lossy.is_empty(),
        "these parse JSON numbers with serde_json's lossy default, one ULP off \
         for roughly one decimal in seven; add features = [\"float_roundtrip\"] \
         to each crate's own manifest: {lossy:?}"
    );
}