kaish-kernel 0.17.1

//! readlink — Print symlink target or resolved path.
//!
//! Without flags, prints the raw symlink target (errors on non-symlinks).
//! With -f, canonicalizes the path by following all symlinks through the VFS.

use async_trait::async_trait;
use clap::{CommandFactory, Parser};
use std::path::Path;

use crate::interpreter::{ExecResult, OutputData};
use crate::tools::{schema_from_clap, ExecContext, ToolCtx, GlobalFlags, Tool, ToolArgs, ToolSchema};

/// Readlink tool: read symlink target or canonicalize a path.
pub struct Readlink;

/// clap-derived argv layer for readlink.
#[derive(Parser, Debug)]
#[command(name = "readlink", about = "Print symlink target or resolved path")]
struct ReadlinkArgs {
    /// Resolve to canonical absolute path (-f)
    #[arg(short = 'f', long = "canonicalize")]
    canonicalize: bool,

    #[command(flatten)]
    global: GlobalFlags,

    /// Symlinks to read.
    paths: Vec<String>,
}

#[async_trait]
impl Tool for Readlink {
    fn name(&self) -> &str {
        "readlink"
    }

    fn schema(&self) -> ToolSchema {
        schema_from_clap(
            &ReadlinkArgs::command(),
            "readlink",
            "Print symlink target or resolved path",
            [
                ("Read symlink target", "readlink link.txt"),
                ("Canonicalize path", "readlink -f ../some/./path"),
            ],
        )
    }

    async fn execute(&self, args: ToolArgs, ctx: &mut dyn ToolCtx) -> ExecResult {
        let Some(ctx) = ctx.as_any_mut().downcast_mut::<ExecContext>() else {
            return ExecResult::failure(1, "internal error: kernel builtin requires ExecContext");
        };
        let argv = match args.to_argv() {
            Ok(v) => v,
            Err(e) => return ExecResult::failure(2, format!("readlink: {e}")),
        };
        let parsed = match ReadlinkArgs::try_parse_from(
            std::iter::once("readlink".to_string()).chain(argv),
        ) {
            Ok(p) => p,
            Err(e) => return ExecResult::failure(2, format!("readlink: {e}")),
        };
        parsed.global.apply(ctx);

        if args.positional.is_empty() {
            return ExecResult::failure(1, "readlink: missing path argument");
        }

        let canonicalize = parsed.canonicalize;
        let mut output = String::new();
        let mut last_err: Option<String> = None;
        let mut exit_code = 0i64;

        for value in &args.positional {
            let path_str = match crate::interpreter::value_to_text_sink_named(value, "a path") {
                Ok(p) => p,
                Err(e) => return ExecResult::failure(1, format!("readlink: {e}")),
            };
            let resolved = ctx.resolve_path(&path_str);

            if canonicalize {
                // GNU readlink -f: canonicalize through symlinks. A missing
                // final component is allowed (the backend resolves parents
                // only); a missing intermediate component still errors.
                match ctx.backend.canonicalize(Path::new(&resolved), true).await {
                    Ok(canonical) => {
                        output.push_str(&canonical.to_string_lossy());
                        output.push('\n');
                    }
                    Err(e) => {
                        last_err = Some(format!("readlink: {}: {}", path_str, e));
                        exit_code = 1;
                    }
                }
                continue;
            }

            // Bare readlink: read the raw symlink target.
            // First check if the path is actually a symlink via lstat; if not,
            // emit the correct "not a symbolic link" message (not the OS EINVAL).
            match ctx.backend.lstat(Path::new(&resolved)).await {
                Ok(entry) => {
                    if !entry.is_symlink() {
                        last_err = Some(format!(
                            "readlink: {}: not a symbolic link",
                            path_str
                        ));
                        exit_code = 1;
                        continue;
                    }
                }
                Err(e) => {
                    use crate::backend::BackendError;
                    last_err = Some(match &e {
                        BackendError::NotFound(_) => {
                            format!("readlink: {}: No such file or directory", path_str)
                        }
                        _ => format!("readlink: {}: {}", path_str, e),
                    });
                    exit_code = 1;
                    continue;
                }
            }

            match ctx.backend.read_link(Path::new(&resolved)).await {
                Ok(target) => {
                    output.push_str(&target.display().to_string());
                    output.push('\n');
                }
                Err(e) => {
                    last_err = Some(format!("readlink: {}: {}", path_str, e));
                    exit_code = 1;
                }
            }
        }

        let mut result = ExecResult::with_output(OutputData::text(output));
        if let Some(msg) = last_err {
            result.err = ExecResult::terminate_diagnostic(msg);
            result = result.with_code(exit_code);
        }
        result
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::ast::Value;
    use crate::vfs::{MemoryFs, VfsRouter};
    use std::sync::Arc;

    fn make_ctx() -> ExecContext {
        let mut vfs = VfsRouter::new();
        vfs.mount("/", MemoryFs::new());
        ExecContext::new(Arc::new(vfs))
    }

    #[tokio::test]
    async fn test_readlink_canonicalize_dotdot_only() {
        let mut ctx = make_ctx();
        let mut args = ToolArgs::new();
        args.positional
            .push(Value::String("/some/../path/./file".into()));
        args.flags.insert("f".to_string());

        let result = Readlink.execute(args, &mut ctx).await;
        // /some/../path/./file normalizes to /path/file; MemoryFs will report
        // "not found" for /path/file, which readlink -f allows as missing final component.
        // The parent /path must also not exist — let's test that the path normalizes at
        // least through the dot-dot without crashing.
        // (The actual test for symlink traversal is in the integration tests.)
        let _ = result; // just confirm it doesn't panic
    }

    #[tokio::test]
    async fn test_readlink_without_flag_on_regular_file_fails() {
        use crate::vfs::Filesystem;

        let mut vfs = VfsRouter::new();
        let mem = MemoryFs::new();
        mem.write(Path::new("regular.txt"), b"content").await.unwrap();
        vfs.mount("/", mem);
        let mut ctx = ExecContext::new(Arc::new(vfs));

        let mut args = ToolArgs::new();
        args.positional.push(Value::String("/regular.txt".into()));

        let result = Readlink.execute(args, &mut ctx).await;
        assert!(!result.ok());
        assert!(result.err.contains("not a symbolic link"), "got: {}", result.err);
    }

    #[tokio::test]
    async fn test_readlink_missing_path() {
        let mut ctx = make_ctx();
        let result = Readlink.execute(ToolArgs::new(), &mut ctx).await;
        assert!(!result.ok());
    }

    async fn make_ctx_with_symlink() -> ExecContext {
        use crate::vfs::Filesystem;

        let mut vfs = VfsRouter::new();
        let mem = MemoryFs::new();

        mem.write(Path::new("target.txt"), b"content").await.unwrap();
        mem.symlink(Path::new("target.txt"), Path::new("link.txt")).await.unwrap();
        mem.symlink(Path::new("nonexistent"), Path::new("broken.txt")).await.unwrap();

        vfs.mount("/", mem);
        ExecContext::new(Arc::new(vfs))
    }

    #[tokio::test]
    async fn test_readlink_symlink_target() {
        let mut ctx = make_ctx_with_symlink().await;
        let mut args = ToolArgs::new();
        args.positional.push(Value::String("/link.txt".into()));

        let result = Readlink.execute(args, &mut ctx).await;
        assert!(result.ok());
        assert_eq!(result.text_out().trim(), "target.txt");
    }

    #[tokio::test]
    async fn test_readlink_on_regular_file() {
        let mut ctx = make_ctx_with_symlink().await;
        let mut args = ToolArgs::new();
        args.positional.push(Value::String("/target.txt".into()));

        let result = Readlink.execute(args, &mut ctx).await;
        assert!(!result.ok());
        assert!(result.err.contains("not a symbolic link"), "got: {}", result.err);
    }

    #[tokio::test]
    async fn test_readlink_broken_symlink() {
        let mut ctx = make_ctx_with_symlink().await;
        let mut args = ToolArgs::new();
        args.positional.push(Value::String("/broken.txt".into()));

        let result = Readlink.execute(args, &mut ctx).await;
        assert!(result.ok());
        assert_eq!(result.text_out().trim(), "nonexistent");
    }

    #[tokio::test]
    async fn test_readlink_not_found() {
        let mut ctx = make_ctx_with_symlink().await;
        let mut args = ToolArgs::new();
        args.positional.push(Value::String("/does-not-exist".into()));

        let result = Readlink.execute(args, &mut ctx).await;
        assert!(!result.ok());
        assert!(result.err.contains("No such file"), "got: {}", result.err);
    }
}