use std::env;

fn main() {
	println!("cargo:rerun-if-changed=build.rs");

	let mut arch_flag_set = false;
	if let Ok(flags) = env::var("MATMULFLAGS") {
		let user_flags = flags.split(',').map(|s| s.trim()).collect::<Vec<_>>();

		let arch_flags = &[
			"arch_generic4x4",
			"arch_generic4x4fma",
			"arch_penryn",
			"arch_sandybridge",
			"arch_haswell",
		];

		let other_flags = &["ftz_daz", "prefetch", "no_multithreading"];

		for user_flag in user_flags.iter() {
			if arch_flags.iter().any(|flag| flag == user_flag) {
				println!("cargo:rustc-cfg={}", user_flag);
				arch_flag_set = true;
			} else if other_flags.iter().any(|flag| flag == user_flag) {
				println!("cargo:rustc-cfg={}", user_flag);
			} else {
				panic!(
					"matrixmultiply_mt: Environment variable MATMULFLAGS contained unrecognised flag: {}",
					user_flag
				);
			}
		}
	} else {
		println!("matrixmultiply_mt: Environment variable MATMULFLAGS was not set");
	}

	// if no architechture specified, take a guess
	if !arch_flag_set {
		if let Ok(features) = env::var("CARGO_CFG_TARGET_FEATURE") {
			println!("matrixmultiply_mt: Guessing CPU architecture from features: {}", features);
			if features.split(',').map(|s| s.trim()).any(|feat| feat == "avx2") {
				println!("cargo:rustc-cfg=arch_haswell");
			} else if features.split(',').map(|s| s.trim()).any(|feat| feat == "avx") {
				println!("cargo:rustc-cfg=arch_sandybridge");
			} else if features.split(',').map(|s| s.trim()).any(|feat| feat == "64bit-mode")
				&& features.split(',').map(|s| s.trim()).any(|feat| feat == "sse")
			{
				println!("cargo:rustc-cfg=arch_penryn");
			} else if features
				.split(',')
				.map(|s| s.trim())
				.any(|feat| feat == "fma" || feat == "fma4")
			{
				println!("cargo:rustc-cfg=generic4x4fma");
			}
		} else {
			println!("matrixmultiply_mt: Cannot guess CPU architecture as CARGO_CFG_TARGET_FEATURE is not available, use environment variable MATMULFLAGS to set arch");
		}
	}
}