//! 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");
    }
}