//! Embeds `migrations/sqlite/*.sql` into the binary.
//!
//! This replaces what `sqlx::migrate!` did as a proc macro. The generated table
//! is `(version, description, sql)`; checksums are computed at runtime rather
//! than baked in, so the manifest test and the runner agree by construction.
//!
//! Filename parsing matches sqlx's exactly -- `<version>_<description>.sql`,
//! with `_` becoming a space in the description -- because the `_sqlx_migrations`
//! ledger in every existing install was written by sqlx and keeps being read and
//! appended to by the runner in `migrate.rs`.

use std::fmt::Write as _;
use std::path::{Path, PathBuf};

fn main() {
    let dir = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("../../migrations/sqlite");
    let dir = dir.canonicalize().unwrap_or(dir);

    // Re-run when a migration is added, removed or edited.
    println!("cargo:rerun-if-changed={}", dir.display());

    let mut entries: Vec<(i64, String, PathBuf)> = Vec::new();
    for entry in std::fs::read_dir(&dir).expect("migrations/sqlite is unreadable") {
        let path = entry.expect("unreadable dir entry").path();
        let Some(name) = path.file_name().and_then(|n| n.to_str()) else {
            continue;
        };
        // sqlx skips anything not matching <version>_<rest>.sql. CHECKSUMS lands here.
        let Some((version, rest)) = name.split_once('_') else {
            continue;
        };
        if !Path::new(rest)
            .extension()
            .is_some_and(|ext| ext.eq_ignore_ascii_case("sql"))
        {
            continue;
        }
        let Ok(version) = version.parse::<i64>() else {
            panic!("migration {name}: expected an integer version prefix");
        };
        let description = rest.trim_end_matches(".sql").replace('_', " ");
        println!("cargo:rerun-if-changed={}", path.display());
        entries.push((version, description, path));
    }

    entries.sort_by_key(|(version, _, _)| *version);
    if let Some(dup) = entries.windows(2).find(|w| w[0].0 == w[1].0) {
        panic!("duplicate migration version {}", dup[0].0);
    }

    let mut out = String::from(
        "// @generated by build.rs from migrations/sqlite. Do not edit.\n\
         pub(crate) static MIGRATIONS: &[(i64, &str, &str)] = &[\n",
    );
    for (version, description, path) in &entries {
        let _ = writeln!(
            out,
            "    ({version}, {description:?}, include_str!({:?})),",
            path.display().to_string()
        );
    }
    out.push_str("];\n");

    let dest = Path::new(&std::env::var("OUT_DIR").expect("OUT_DIR unset")).join("migrations.rs");
    std::fs::write(&dest, out).expect("failed to write generated migrations");
}