//! What the runtime bundle (`bundle`, which `export` turns on) is made from: the flowRS commit
//! it names (`runtime::REV`), and the source of the crates it carries.
//!
//! **The commit.** An exported project carries flowRS's runtime crates in `vendor/`, copied
//! from the source this exporter was built from, and its `vendor/README.md` names that commit.
//! The revision is `FLOWRS_EXPORT_REV` when the build sets it, else this checkout's HEAD. A
//! HEAD that changes nothing over its parent (the commit a build host makes of a clean
//! worktree it snapshots) names the parent, the commit that is in flowRS's history.
//!
//! **The source.** Every text file of the crates the bundle may carry (their sources, assets,
//! manifests, licences, notices and provenance; not their tests, examples, benches, fuzzers,
//! fixtures or eval corpora), the workspace's manifest and its `Cargo.lock`, compiled in with
//! `include_str!` (`$OUT_DIR/runtime_sources.rs`). Which of them go into `vendor/`, and how the
//! manifests are rewritten to stand alone, is `runtime.rs`'s to decide, where it is tested;
//! this script only lists files. A generated project, which links the shell alone, runs
//! nothing here.

use std::path::{Path, PathBuf};
use std::process::Command;

/// The crates the bundle may carry: `runtime::RULES` names the same, and a test holds the two
/// together.
const CRATES: &[&str] = &[
    "flowrs-openui",
    "flowrs-app",
    "flowrs-appshell",
    "flowrs-math",
    "flowrs-dsp",
    "flowrs-sequence",
    "flowrs-record",
    "flowrs-results",
    "flowrs-station",
    "flowrs-transport",
    "flowrs-hal",
    "flowrs-device",
];

/// Directories at a crate's top level that never go into a vendored crate.
const SKIP_DIRS: &[&str] = &[
    "target", "tests", "benches", "examples", "fuzz", "eval", "fixtures",
];

fn git(dir: &Path, args: &[&str]) -> Option<String> {
    let out = Command::new("git")
        .arg("-C")
        .arg(dir)
        .args(args)
        .output()
        .ok()?;
    if !out.status.success() {
        return None;
    }
    let s = String::from_utf8(out.stdout).ok()?.trim().to_string();
    (!s.is_empty()).then_some(s)
}

fn rev(dir: &Path) -> String {
    let given = std::env::var("FLOWRS_EXPORT_REV")
        .ok()
        .map(|s| s.trim().to_string())
        .filter(|s| !s.is_empty());
    let rev = given.or_else(|| {
        // Rebuild when HEAD moves: the worktree's HEAD, the branch it names, packed refs.
        if let Some(git_dir) = git(dir, &["rev-parse", "--absolute-git-dir"]) {
            println!("cargo:rerun-if-changed={git_dir}/HEAD");
            if let Some(common) = git(dir, &["rev-parse", "--git-common-dir"]) {
                let common = if Path::new(&common).is_absolute() {
                    common
                } else {
                    dir.join(&common).to_string_lossy().into_owned()
                };
                println!("cargo:rerun-if-changed={common}/packed-refs");
                if let Some(head_ref) = git(dir, &["symbolic-ref", "-q", "HEAD"]) {
                    println!("cargo:rerun-if-changed={common}/{head_ref}");
                }
            }
        }
        let head = git(dir, &["rev-parse", "HEAD"])?;
        let tree = git(dir, &["rev-parse", "HEAD^{tree}"]);
        let parent_tree = git(dir, &["rev-parse", "HEAD~1^{tree}"]);
        match (tree, parent_tree) {
            (Some(t), Some(p)) if t == p => git(dir, &["rev-parse", "HEAD~1"]).or(Some(head)),
            _ => Some(head),
        }
    });
    // Without git and without the variable: said so, in the README of every project.
    rev.unwrap_or_else(|| "unknown".into())
}

/// Every text file under `dir`, as paths relative to `root`, sorted. Hidden entries and the
/// skipped top-level directories are left out; a file that is not UTF-8 is too (no crate the
/// bundle carries compiles one in).
fn files(root: &Path, dir: &Path, out: &mut Vec<(String, PathBuf)>) {
    let Ok(entries) = std::fs::read_dir(dir) else {
        return;
    };
    let mut entries: Vec<_> = entries.filter_map(Result::ok).collect();
    entries.sort_by_key(|e| e.file_name());
    for e in entries {
        let name = e.file_name().to_string_lossy().into_owned();
        if name.starts_with('.') {
            continue;
        }
        let path = e.path();
        let rel = path
            .strip_prefix(root)
            .map(|p| p.to_string_lossy().replace('\\', "/"))
            .unwrap_or_default();
        if path.is_dir() {
            if dir == root && SKIP_DIRS.contains(&name.as_str()) {
                continue;
            }
            files(root, &path, out);
        } else if std::fs::read_to_string(&path).is_ok() {
            out.push((rel, path));
        }
    }
}

fn main() {
    println!("cargo:rerun-if-env-changed=FLOWRS_EXPORT_REV");
    println!("cargo:rerun-if-changed=build.rs");
    if std::env::var_os("CARGO_FEATURE_BUNDLE").is_none() {
        return;
    }
    let dir = PathBuf::from(std::env::var("CARGO_MANIFEST_DIR").unwrap_or_default());
    println!("cargo:rustc-env=FLOWRS_EXPORT_REV={}", rev(&dir));

    let crates_dir = dir.join("..");
    let root = dir.join("../..");
    let mut src = String::from(
        "/// Each file the bundle may carry: (crate, path within it, contents).\n\
         pub(crate) static SOURCES: &[(&str, &str, &str)] = &[\n",
    );
    for name in CRATES {
        let crate_dir = crates_dir.join(name);
        println!("cargo:rerun-if-changed={}", crate_dir.display());
        let mut found = Vec::new();
        files(&crate_dir, &crate_dir, &mut found);
        for (rel, path) in found {
            let abs = std::fs::canonicalize(&path).unwrap_or(path);
            src.push_str(&format!(
                "    ({name:?}, {rel:?}, include_str!({:?})),\n",
                abs.to_string_lossy()
            ));
        }
    }
    src.push_str("];\n");
    // The public engine carries a lock pruned to its own crates; what an export pins is what
    // flowRS's whole workspace pins, so there the full lock travels beside the lock data.
    let full_lock = dir.join("data/export-cargo.lock");
    let lockfile = if full_lock.exists() {
        full_lock
    } else {
        root.join("Cargo.lock")
    };
    for (constant, file, path) in [
        ("WORKSPACE_MANIFEST", "Cargo.toml", root.join("Cargo.toml")),
        ("LOCKFILE", "Cargo.lock", lockfile),
    ] {
        println!("cargo:rerun-if-changed={}", path.display());
        let abs = std::fs::canonicalize(&path).unwrap_or(path);
        src.push_str(&format!(
            "/// The workspace's `{file}`.\npub(crate) static {constant}: &str = include_str!({:?});\n",
            abs.to_string_lossy()
        ));
    }
    let out = PathBuf::from(std::env::var("OUT_DIR").unwrap_or_default());
    std::fs::write(out.join("runtime_sources.rs"), src).expect("write runtime_sources.rs");
}