use std::fs;
use std::path::Path;

fn main() {
    let migrations = Path::new("migrations");
    println!("cargo:rerun-if-changed={}", migrations.display());

    let mut count = 0u64;
    if let Ok(entries) = fs::read_dir(migrations) {
        for entry in entries.flatten() {
            let path = entry.path();
            if path.extension().is_some_and(|extension| extension == "sql") {
                println!("cargo:rerun-if-changed={}", path.display());
                // 将文件大小加入计数，确保新增/删除/修改文件都改变输出
                count = count.wrapping_add(fs::metadata(&path).map(|m| m.len()).unwrap_or(0));
            }
        }
    }

    // 将 migration 摘要写入 OUT_DIR，lib.rs 通过 include! 引用。
    // 这样 cargo 可以追踪 migration 变更 → lib.rs 重编译 → sqlx::migrate! 重新展开。
    let out_dir = std::env::var("OUT_DIR").unwrap();
    let dest = Path::new(&out_dir).join("migration_stamp.rs");
    fs::write(
        &dest,
        format!("// generated by build.rs\npub const MIGRATION_STAMP: u64 = {count};\n"),
    )
    .unwrap();
}