openmoat 0.10.0

//! Environment and filesystem access: everything `openmoat-core` must not do itself.

use std::fs;
use std::io::Read as _;
use std::path::{Component, Path, PathBuf};

use anyhow::{Context as _, Result, bail};
use openmoat_core::{EvalContext, Policy};
use openmoat_hosts::Host;

use crate::home;
use crate::project;

/// Largest policy file accepted. Policies are human-written; anything bigger is
/// a mistake or an attack on the loader.
const MAX_POLICY_BYTES: u64 = 1024 * 1024;

/// Read and lint a policy file.
pub fn load_policy(path: &Path) -> Result<Policy> {
    Policy::parse(&read_policy(path)?).with_context(|| format!("invalid policy {}", path.display()))
}

/// Parse and lint the policy in `bytes`, already read from `path` (named in
/// errors), with the limits [`read_policy`] applies. `moat guard` passes the
/// bytes the lock check verified, so the policy it decides by is the pinned one.
pub fn parse_policy(bytes: Vec<u8>, path: &Path) -> Result<Policy> {
    let size = bytes.len();
    if u64::try_from(size).map_or(true, |size| size > MAX_POLICY_BYTES) {
        bail!(
            "policy {} is {size} bytes; the limit is {MAX_POLICY_BYTES}",
            path.display()
        );
    }
    let text = String::from_utf8(bytes)
        .with_context(|| format!("reading policy {} (must be UTF-8)", path.display()))?;
    Policy::parse(&text).with_context(|| format!("invalid policy {}", path.display()))
}

/// The text of a policy file, at most [`MAX_POLICY_BYTES`] of UTF-8.
pub fn read_policy(path: &Path) -> Result<String> {
    let file =
        fs::File::open(path).with_context(|| format!("opening policy {}", path.display()))?;
    let size = file
        .metadata()
        .with_context(|| format!("reading metadata of {}", path.display()))?
        .len();
    if size > MAX_POLICY_BYTES {
        bail!(
            "policy {} is {size} bytes; the limit is {MAX_POLICY_BYTES}",
            path.display()
        );
    }
    let mut text = String::with_capacity(usize::try_from(size).unwrap_or(0));
    file.take(MAX_POLICY_BYTES)
        .read_to_string(&mut text)
        .with_context(|| format!("reading policy {} (must be UTF-8)", path.display()))?;
    Ok(text)
}

/// Build the evaluation context from explicit flags and the process environment.
/// The project root defaults to the git root above `cwd` (`project::root_of`);
/// an explicit `project` that could never be trusted is an error, not a
/// silent change of meaning.
pub fn eval_context(
    state: &home::Home,
    cwd: Option<&Path>,
    project: Option<&Path>,
) -> Result<EvalContext> {
    let cwd = match cwd {
        Some(dir) => absolute(dir)?,
        None => std::env::current_dir().context("determining the current directory")?,
    };
    let home = home::user_home()?;
    let project = match project {
        Some(dir) => {
            let dir = absolute(dir)?;
            if !project::trusted(&dir, &home) {
                bail!(
                    "{} cannot be a project root: it is the home directory, one of its \
                     ancestors or a filesystem root",
                    dir.display()
                );
            }
            Some(dir)
        }
        None => project::root_of(&cwd, &home),
    };
    let home = path_string(&home);
    let project = project.as_deref().map(path_string);
    Ok(EvalContext {
        real_home: real_root(&home),
        real_project: project.as_deref().and_then(real_root),
        moved_dirs: moved_dirs(state)?,
        home,
        project,
        cwd: path_string(&cwd),
        case_insensitive_paths: CASE_INSENSITIVE_PATHS,
    })
}

/// The home directory as written and with its symlinks resolved (when that
/// differs), the spellings host-wide sandbox settings must cover.
pub fn home_spellings() -> Result<(String, Option<String>)> {
    let home = path_string(&home::user_home()?);
    let real = real_root(&home);
    Ok((home, real))
}

/// The state and host directories moved out of the home directory: the one each
/// environment variable names and the host directory `moat init` recorded
/// (`hosts.json`), both when they differ, since an agent may run with either.
/// Each as written and with its symlinks resolved, so rules naming the default
/// directory (`kernel-self`) protect the moved ones too.
pub fn moved_dirs(state: &home::Home) -> Result<Vec<(String, String)>> {
    let recorded = crate::install::Recorded::load(state)?;
    let mut out = Vec::new();
    let mut dirs = vec![(home::DIR_NAME, env_dir(home::ENV), None)];
    // A host's own location rules do more than name a directory (`custom_moved`).
    for host in Host::ALL
        .into_iter()
        .filter(|h| crate::install::location::custom(*h).is_none())
    {
        let name = crate::install::dir_variable(host)?.1;
        dirs.push((name, crate::install::env_config_dir(host)?, Some(host)));
    }
    let mut add = |default: &str, dir: &Path| -> Result<()> {
        let dir = path_string(&absolute(dir)?);
        for spelling in real_root(&dir).into_iter().chain([dir]) {
            let pair = (default.to_owned(), spelling);
            if !out.contains(&pair) {
                out.push(pair);
            }
        }
        Ok(())
    };
    for (name, from_env, host) in dirs {
        let default = format!("~/{name}");
        let at_home = home::user_home()?.join(name);
        let from_record = host.and_then(|h| recorded.dir(h)).filter(|d| *d != at_home);
        for dir in from_env.into_iter().chain(from_record) {
            add(&default, &dir)?;
        }
    }
    for host in Host::ALL {
        for (default, dir) in custom_moved(&recorded, host)? {
            add(&default, &dir)?;
        }
    }
    Ok(out)
}

fn env_dir(var: &str) -> Option<PathBuf> {
    std::env::var_os(var)
        .filter(|v| !v.is_empty())
        .map(PathBuf::from)
}

/// The configuration directory and hook file of a host with its own location
/// rules (OpenClaw's state directory and `openclaw.json`) where this shell's
/// environment or `moat init`'s record puts them, each paired with the
/// default it replaces when it is not there; empty for any other host.
fn custom_moved(recorded: &crate::install::Recorded, host: Host) -> Result<Vec<(String, PathBuf)>> {
    use crate::install::location;
    let (Some(locate), Some(install)) = (location::custom(host), host.spec().install.as_ref())
    else {
        return Ok(Vec::new());
    };
    let mut locations: Vec<_> = location::from_env(locate)?.into_iter().collect();
    if let Some(dir) = recorded.dir(host) {
        locations.push(locate.at(dir, recorded.file(host)));
    }
    let default = locate.default_for(&home::user_home()?);
    let (dir_name, file) = (install.dir_name, install.config_file);
    let mut out = Vec::new();
    for located in locations {
        if located.dir != default.dir {
            out.push((format!("~/{dir_name}"), located.dir.clone()));
        }
        if !locate.config_is_default(&located) {
            out.push((format!("~/{dir_name}/{file}"), located.config));
        }
    }
    Ok(out)
}

/// `root` with its symlinks resolved, when that differs from `root`: the form
/// the path resolver reports paths under it in (`realpath.rs`).
fn real_root(root: &str) -> Option<String> {
    let real = path_string(&fs::canonicalize(root).ok()?);
    (real != root).then_some(real)
}

/// Absolute and lexically normalised (`.` and `..` removed) without touching
/// the filesystem, the way `guard` takes the host's `cwd`.
///
/// `--project` and `--cwd` must name directories the same way the checked
/// action does: canonicalising only the roots turned `/tmp/p` into
/// `/private/tmp/p` on macOS and `RUNNER~1` into the long name on Windows, so
/// a file inside the project no longer matched `${project}/**`.
pub fn absolute(path: &Path) -> Result<PathBuf> {
    let absolute =
        std::path::absolute(path).with_context(|| format!("resolving {}", path.display()))?;
    let mut normalised = PathBuf::new();
    for component in absolute.components() {
        match component {
            Component::CurDir => {}
            Component::ParentDir => {
                normalised.pop();
            }
            other => normalised.push(other),
        }
    }
    Ok(normalised)
}

/// Default file systems on macOS (APFS) and Windows (NTFS) ignore case, so
/// `~/.SSH/id_rsa` names the same file as `~/.ssh/id_rsa` there.
pub const CASE_INSENSITIVE_PATHS: bool = cfg!(any(target_os = "macos", windows));

/// The slash-separated canonical form the core works in (`docs/POLICY.md` §3.2).
pub fn path_string(path: &Path) -> String {
    slash_form(&path.to_string_lossy(), cfg!(windows))
}

/// On Windows: drop the verbatim prefix `canonicalize` adds (`\\?\C:\x`,
/// `\\?\UNC\srv\share`), which the core would read as a UNC path named `?`,
/// then use `/` as the separator.
fn slash_form(text: &str, windows: bool) -> String {
    if windows {
        strip_verbatim(text).replace('\\', "/")
    } else {
        text.to_owned()
    }
}

pub fn strip_verbatim(text: &str) -> String {
    if let Some(unc) = text.strip_prefix(r"\\?\UNC\") {
        format!(r"\\{unc}")
    } else {
        text.strip_prefix(r"\\?\").unwrap_or(text).to_owned()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn roots_are_made_absolute_lexically() {
        let base = std::env::current_dir().unwrap();
        assert_eq!(
            absolute(Path::new("a/./b/../c")).unwrap(),
            base.join("a").join("c")
        );
        let root = base.ancestors().last().unwrap();
        assert_eq!(absolute(&root.join("..")).unwrap(), root);
    }

    #[test]
    fn policy_bytes_get_the_limits_of_a_policy_file() {
        let path = Path::new("policy.yaml");
        let big = vec![b' '; usize::try_from(MAX_POLICY_BYTES).unwrap() + 1];
        assert!(format!("{:#}", parse_policy(big, path).unwrap_err()).contains("the limit is"));
        let latin1 = b"version: 1\n# na\xefve\n".to_vec();
        assert!(format!("{:#}", parse_policy(latin1, path).unwrap_err()).contains("UTF-8"));
        let text = openmoat_core::DEFAULT_POLICY;
        assert_eq!(
            parse_policy(text.as_bytes().to_vec(), path).unwrap(),
            Policy::parse(text).unwrap()
        );
    }

    #[test]
    fn windows_verbatim_paths_become_canonical_slash_form() {
        assert_eq!(slash_form(r"\\?\C:\p\src", true), "C:/p/src");
        assert_eq!(slash_form(r"\\?\UNC\srv\share\x", true), "//srv/share/x");
        assert_eq!(slash_form(r"C:\p", true), "C:/p");
        assert_eq!(slash_form("/Users/me/p", false), "/Users/me/p");
        assert_eq!(strip_verbatim(r"\\?\C:\p"), r"C:\p");
    }
}