use std::env;
use std::path::PathBuf;

const LIBRARY_DIR_VARIABLE: &str = "VAPOURSYNTH_LIB_DIR";

fn main() {
    // Make sure the build script is re-run if our env variable is changed.
    println!("cargo:rerun-if-env-changed={}", LIBRARY_DIR_VARIABLE);

    let windows = env::var("TARGET").unwrap().contains("windows");

    // Get the default library dir on Windows.
    let default_library_dir = if windows {
        get_default_library_dir()
    } else {
        None
    };

    // Library directory override or the default dir on windows.
    if let Some(dir) = env::var(LIBRARY_DIR_VARIABLE).ok().or(default_library_dir) {
        println!("cargo:rustc-link-search=native={}", dir);
    }

    // Handle linking to VapourSynth libs.
    if env::var("CARGO_FEATURE_VAPOURSYNTH_FUNCTIONS").is_ok() {
        println!("cargo:rustc-link-lib=vapoursynth");
    }

    if env::var("CARGO_FEATURE_VSSCRIPT_FUNCTIONS").is_ok() {
        let vsscript_lib_name = if windows {
            "vsscript"
        } else {
            "vapoursynth-script"
        };

        println!("cargo:rustc-link-lib={}", vsscript_lib_name);
    }
}

// Returns the default library dir on Windows.
// The default dir is where the VapourSynth installer puts the libraries.
fn get_default_library_dir() -> Option<String> {
    let host = env::var("HOST").ok()?;

    // If the host isn't Windows we don't have %programfiles%.
    if !host.contains("windows") {
        return None;
    }

    let programfiles = if host.starts_with("i686") {
        env::var("programfiles")
    } else {
        env::var("programfiles(x86)")
    };

    let suffix = if env::var("TARGET").ok()?.starts_with("i686") {
        "lib32"
    } else {
        "lib64"
    };

    let mut path = PathBuf::from(programfiles.ok()?);
    path.push("VapourSynth");
    path.push("sdk");
    path.push(suffix);
    path.to_str().map(|s| s.to_owned())
}