//! OxygenFlow's cheap checks as one WASI module (#96): what

//! `.flow/jobs/{layout,todos,size,summary}.sh` did in an Alpine microVM, so

//! that any runner offering the WASM tier (a phone, plex, windows-1) can take

//! them. The job's files are preopened as `/src`, which is also the current

//! directory, so every path here is relative to the workspace.

//!

//! - `layout PATH...`: each path is a file; fails naming the first missing.

//! - `todos DIR...`: the lines holding a note marker, counted, the first 20

//!   listed; never fails.

//! - `size DIR`: lines of Rust in each crate directory under DIR.

//! - `summary`: one line naming `$PROJECT`.

use std::fs;

use std::io::{self, Write};

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

use std::process::ExitCode;

/// The note markers, spelt in pieces so this file does not count itself.

const MARKERS: [&str; 3] = [concat!("TO", "DO"), concat!("FIX", "ME"), concat!("X", "XX")];

/// How many noted lines `todos` lists.

const LISTED: usize = 20;

const USAGE: &str = "usage: flow-checks layout PATH... | todos DIR... | size DIR | summary";

fn main() -> ExitCode {

    let args: Vec<String> = std::env::args().skip(1).collect();

    let root = Path::new(".");

    let mut out = io::stdout().lock();

    let done = match args.split_first() {

        Some((cmd, rest)) => match cmd.as_str() {

            "layout" => layout(root, rest, &mut out),

            "todos" => todos(root, rest, &mut out),

            "size" => match rest {

                [dir] => size(root, dir, &mut out),

                _ => Err(USAGE.to_string()),

            },

            "summary" => summary(std::env::var("PROJECT").ok().as_deref(), &mut out),

            _ => Err(USAGE.to_string()),

        },

        None => Err(USAGE.to_string()),

    };

    match done {

        Ok(()) => ExitCode::SUCCESS,

        Err(e) => {

            eprintln!("{e}");

            ExitCode::FAILURE

        }

    }

}

type Done = Result<(), String>;

fn emit(out: &mut impl Write, line: &str) -> Done {

    writeln!(out, "{line}").map_err(|e| format!("write: {e}"))

}

/// The workspace has the files it should.

fn layout(root: &Path, paths: &[String], out: &mut impl Write) -> Done {

    if paths.is_empty() {

        return Err(USAGE.to_string());

    }

    for p in paths {

        if !root.join(p).is_file() {

            return Err(format!("missing: {p}"));

        }

        emit(out, &format!("found {p}"))?;

    }

    Ok(())

}

/// Notes left in the code, for the log.

fn todos(root: &Path, dirs: &[String], out: &mut impl Write) -> Done {

    if dirs.is_empty() {

        return Err(USAGE.to_string());

    }

    let mut noted = Vec::new();

    for d in dirs {

        for file in files(&root.join(d))? {

            // Text only, as grep reports a binary file rather than its lines.

            let Ok(text) = fs::read_to_string(&file) else { continue };

            let name = shown(root, &file);

            for (i, line) in text.lines().enumerate() {

                if MARKERS.iter().any(|m| line.contains(m)) {

                    noted.push(format!("{name}:{}:{line}", i + 1));

                }

            }

        }

    }

    emit(out, &format!("{} {} notes in {}", noted.len(), MARKERS.join("/"), shown_dirs(dirs)))?;

    for line in noted.iter().take(LISTED) {

        emit(out, line)?;

    }

    Ok(())

}

/// Lines of Rust per crate: each directory directly under `dir`.

fn size(root: &Path, dir: &str, out: &mut impl Write) -> Done {

    for krate in entries(&root.join(dir))?.into_iter().filter(|p| p.is_dir()) {

        let mut lines = 0;

        for file in files(&krate)?.into_iter().filter(|f| f.extension().is_some_and(|e| e == "rs")) {

            let bytes = fs::read(&file).map_err(|e| format!("{}: {e}", file.display()))?;

            lines += bytes.iter().filter(|&&b| b == b'\n').count();

        }

        emit(out, &format!("{:<24} {lines:>6} lines", format!("{}/", shown(root, &krate))))?;

    }

    Ok(())

}

fn summary(project: Option<&str>, out: &mut impl Write) -> Done {

    emit(out, &format!("{}: every check passed on this state.", project.unwrap_or("This project")))

}

/// A directory's entries, sorted by name so every runner prints the same.

fn entries(dir: &Path) -> Result<Vec<PathBuf>, String> {

    let read = fs::read_dir(dir).map_err(|e| format!("{}: {e}", dir.display()))?;

    let mut all = read.map(|e| e.map(|e| e.path())).collect::<Result<Vec<_>, _>>().map_err(|e| format!("{}: {e}", dir.display()))?;

    all.sort();

    Ok(all)

}

/// Every file under `dir`, depth first, in name order; links are not followed.

fn files(dir: &Path) -> Result<Vec<PathBuf>, String> {

    let mut found = Vec::new();

    for p in entries(dir)? {

        let kind = fs::symlink_metadata(&p).map_err(|e| format!("{}: {e}", p.display()))?.file_type();

        if kind.is_dir() {

            found.extend(files(&p)?);

        } else if kind.is_file() {

            found.push(p);

        }

    }

    Ok(found)

}

/// A path as the workspace names it, with `/` between its parts.

fn shown(root: &Path, p: &Path) -> String {

    let rel = p.strip_prefix(root).unwrap_or(p);

    rel.components().map(|c| c.as_os_str().to_string_lossy()).collect::<Vec<_>>().join("/")

}

fn shown_dirs(dirs: &[String]) -> String {

    dirs.iter().map(|d| format!("{}/", d.trim_end_matches('/'))).collect::<Vec<_>>().join(" ")

}

#[cfg(test)]

mod tests {

    use super::*;

    fn tree(files: &[(&str, &str)]) -> tempfile::TempDir {

        let dir = tempfile::tempdir().unwrap();

        for (path, text) in files {

            let p = dir.path().join(path);

            fs::create_dir_all(p.parent().unwrap()).unwrap();

            fs::write(p, text).unwrap();

        }

        dir

    }

    fn run(f: impl FnOnce(&mut Vec<u8>) -> Done) -> (Done, String) {

        let mut out = Vec::new();

        let done = f(&mut out);

        (done, String::from_utf8(out).unwrap())

    }

    fn args(a: &[&str]) -> Vec<String> {

        a.iter().map(|s| s.to_string()).collect()

    }

    #[test]

    fn layout_lists_what_it_found_and_fails_on_the_first_missing() {

        let t = tree(&[("Cargo.toml", ""), ("docs/m0.md", "")]);

        let (done, out) = run(|o| layout(t.path(), &args(&["Cargo.toml", "docs/m0.md"]), o));

        assert_eq!(done, Ok(()));

        assert_eq!(out, "found Cargo.toml\nfound docs/m0.md\n");

        let (done, out) = run(|o| layout(t.path(), &args(&["Cargo.toml", "nope.rs", "docs/m0.md"]), o));

        assert_eq!(done, Err("missing: nope.rs".to_string()));

        assert_eq!(out, "found Cargo.toml\n");

        // A directory is not the file asked for.

        assert!(layout(t.path(), &args(&["docs"]), &mut Vec::new()).is_err());

    }

    #[test]

    fn todos_counts_every_marked_line_and_lists_the_first_twenty() {

        let marker = MARKERS[0];

        let many: String = (0..25).map(|i| format!("// {marker} {i}\n")).collect();

        let t = tree(&[

            ("crates/a/src/lib.rs", &format!("fn a() {{}}\n// {} later\n", MARKERS[1])),

            ("crates/b/src/many.rs", &many),

            ("crates/b/blob.bin", "\u{0}"),

        ]);

        // Invalid UTF-8 is skipped, as grep skips a binary file's lines.

        fs::write(t.path().join("crates/b/blob.bin"), [0xff, 0xfe, b'T']).unwrap();

        let (done, out) = run(|o| todos(t.path(), &args(&["crates"]), o));

        assert_eq!(done, Ok(()));

        let lines: Vec<&str> = out.lines().collect();

        assert_eq!(lines[0], format!("26 {} notes in crates/", MARKERS.join("/")));

        assert_eq!(lines[1], format!("crates/a/src/lib.rs:2:// {} later", MARKERS[1]));

        assert_eq!(lines[2], format!("crates/b/src/many.rs:1:// {marker} 0"));

        assert_eq!(lines.len(), 1 + LISTED);

    }

    #[test]

    fn size_counts_rust_lines_per_crate_in_name_order() {

        let t = tree(&[

            ("crates/zeta/src/main.rs", "a\nb\nc\n"),

            ("crates/alpha/src/lib.rs", "a\n"),

            ("crates/alpha/src/deep/mod.rs", "a\nb\n"),

            ("crates/alpha/README.md", "not rust\n"),

            ("crates/loose.txt", "a file, not a crate\n"),

        ]);

        let (done, out) = run(|o| size(t.path(), "crates", o));

        assert_eq!(done, Ok(()));

        assert_eq!(out, format!("{:<24} {:>6} lines\n{:<24} {:>6} lines\n", "crates/alpha/", 3, "crates/zeta/", 3));

    }

    #[test]

    fn summary_names_the_project() {

        let (_, out) = run(|o| summary(Some("OxygenFlow"), o));

        assert_eq!(out, "OxygenFlow: every check passed on this state.\n");

    }

}