use std::path::{Path, PathBuf};
use std::{env, fs};

fn main() {
    if let Some(git_sha) = read_git_sha() {
        println!("cargo:rustc-env={}={}", "BUILD_SHA", git_sha);
    }

    if web_playground_files_present() {
        println!("cargo:rustc-cfg={}", "TREE_SITTER_EMBED_WASM_BINDING");
    }

    let rust_binding_version = read_rust_binding_version();
    println!(
        "cargo:rustc-env={}={}",
        "RUST_BINDING_VERSION", rust_binding_version,
    );

    let emscripten_version = fs::read_to_string("emscripten-version").unwrap();
    println!(
        "cargo:rustc-env={}={}",
        "EMSCRIPTEN_VERSION", emscripten_version,
    );
}

fn web_playground_files_present() -> bool {
    let paths = [
        "../docs/assets/js/playground.js",
        "../lib/binding_web/tree-sitter.js",
        "../lib/binding_web/tree-sitter.wasm",
    ];

    paths.iter().all(|p| Path::new(p).exists())
}

fn read_git_sha() -> Option<String> {
    let mut repo_path = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());

    let mut git_path;
    loop {
        git_path = repo_path.join(".git");
        if git_path.exists() {
            break;
        } else if !repo_path.pop() {
            return None;
        }
    }

    let git_dir_path;
    if git_path.is_dir() {
        git_dir_path = git_path;
    } else if let Ok(git_path_content) = fs::read_to_string(&git_path) {
        git_dir_path = repo_path.join(git_path_content.get("gitdir: ".len()..).unwrap().trim_end());
    } else {
        return None;
    }
    let git_head_path = git_dir_path.join("HEAD");
    if let Some(path) = git_head_path.to_str() {
        println!("cargo:rerun-if-changed={}", path);
    }
    if let Ok(mut head_content) = fs::read_to_string(&git_head_path) {
        if head_content.ends_with("\n") {
            head_content.pop();
        }

        // If we're on a branch, read the SHA from the ref file.
        if head_content.starts_with("ref: ") {
            head_content.replace_range(0.."ref: ".len(), "");
            let ref_filename = git_dir_path.join(&head_content);
            if let Some(path) = ref_filename.to_str() {
                println!("cargo:rerun-if-changed={}", path);
            }
            return fs::read_to_string(&ref_filename).ok();
        }
        // If we're on a detached commit, then the `HEAD` file itself contains the sha.
        else if head_content.len() == 40 {
            return Some(head_content);
        }
    }

    None
}

fn read_rust_binding_version() -> String {
    let path = "Cargo.toml";
    let text = fs::read_to_string(path).unwrap();
    let cargo_toml = toml::from_str::<toml::Value>(text.as_ref()).unwrap();
    cargo_toml["dependencies"]["tree-sitter"]["version"]
        .as_str()
        .unwrap()
        .trim_matches('"')
        .to_string()
}
