kaish-kernel 0.16.0

//! write — Write content to a file.

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

use crate::ast::Value;
use crate::interpreter::{ExecResult, OutputData};
use crate::operation::KernelOperation;
use crate::tools::builtin::get_path_string;
use crate::tools::{schema_from_clap, ExecContext, ToolCtx, GlobalFlags, Tool, ToolArgs, ToolSchema};

/// Write tool: write content to a file.
pub struct Write;

/// clap-derived argv layer for write.
#[derive(Parser, Debug)]
#[command(name = "write", about = "Write content to a file")]
struct WriteArgs {
    /// File path to write to (positional or --path).
    #[arg(long)]
    path: Option<String>,

    /// Content to write (positional or --content). Falls back to stdin when absent.
    #[arg(long)]
    content: Option<String>,


    #[command(flatten)]
    global: GlobalFlags,

    /// Destination path followed by the content to write.
    args: Vec<String>,
}

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

    fn schema(&self) -> ToolSchema {
        schema_from_clap(
            &WriteArgs::command(),
            "write",
            "Write content to a file",
            [
                ("Write to a file", "write output.txt \"hello world\""),
                ("Pipe into write", "echo content | write file.txt"),
            ],
        )
        .with_operations([KernelOperation::FsOverwrite.as_str()])
    }

    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");
        };
        // `--content` is never read off `parsed.content` — see below, it's
        // always read as a raw typed `Value` off `args.named`/`args.positional`
        // specifically so a `Value::Bytes` payload survives untouched. That
        // makes it the same "clap sink nobody reads" case as `push`'s hidden
        // positional (CLAUDE.md's clap-builtin convention), just on a named
        // flag instead: `to_argv()`'s loud named-Bytes guard (GH #164) exists
        // for keys a builtin *does* read via the clap-parsed field, so
        // exclude `content` from argv (GH #218's `to_argv_excluding` — a
        // first-class alternative to hand-cloning `ToolArgs` and removing the
        // key). Every other flag (`path`/global) still gets the full guard,
        // and `parsed.content` simply stays `None`, which is fine since
        // nothing reads it.
        let argv = match args.to_argv_excluding(&["content"]) {
            Ok(v) => v,
            Err(e) => return ExecResult::failure(2, format!("write: {e}")),
        };
        let parsed = match WriteArgs::try_parse_from(
            std::iter::once("write".to_string()).chain(argv),
        ) {
            Ok(p) => p,
            Err(e) => return ExecResult::failure(2, format!("write: {e}")),
        };
        parsed.global.apply(ctx);

        let path = match get_path_string(&args, "path", 0) {
            Ok(Some(p)) => p,
            Ok(None) => return ExecResult::failure(1, "write: missing path argument"),
            Err(e) => return ExecResult::failure(1, format!("write: {e}")),
        };

        let resolved = ctx.resolve_path(&path);

        // Under trash, the truncating overwrite snapshots the prior content,
        // returned for the CAS below (no-op with trash off).
        let snapshots = match ctx
            .snapshot_overwrites("write",
                &[(path.clone(), false)])
            .await
        {
            Ok(s) => s,
            Err(blocked) => return blocked,
        };

        // Content can be positional[1], named "content", or stdin. Read it as
        // raw bytes so a `Value::Bytes` (e.g. from `$(producer)`) is written
        // verbatim instead of stringified to the `[binary: N bytes]` marker —
        // that placeholder reaching a file is silent corruption. Stdin uses the
        // byte reader (pipe-preferred) for the same reason.
        let content: Vec<u8> = if let Some(v) = args.named.get("content") {
            value_to_bytes(v)
        } else if let Some(v) = args.positional.get(1) {
            value_to_bytes(v)
        } else {
            // Zero bytes mean "write an empty file" only when something
            // deliberately supplied them — an upstream stage, a redirect, an
            // embedder buffer. The session's own stdin did not: `write f`
            // reading from /dev/null is a missing operand, and writing it
            // destroys the file it was pointed at.
            let content_was_offered = ctx.stdin.is_some()
                || ctx.pipeline_position != crate::dispatch::PipelinePosition::Only;
            match ctx.read_stdin_to_bytes().await {
                Ok(Some(bytes)) if bytes.is_empty() && !content_was_offered => {
                    return ExecResult::failure(1, missing_content_error(&path))
                }
                Ok(Some(bytes)) => bytes,
                Ok(None) => return ExecResult::failure(1, missing_content_error(&path)),
                Err(e) => return ExecResult::failure(1, format!("write: {e}")),
            }
        };

        // CAS against the gate snapshot: a concurrent change between the gate
        // and this write is a loud conflict, not a silent clobber.
        let expected = snapshots.get(&resolved);
        match ctx.overwrite_checked(Path::new(&resolved), &content, expected).await {
            Ok(()) => ExecResult::with_output(OutputData::text(format!("Wrote {} bytes to {}", content.len(), path))),
            Err(e) => ExecResult::failure(1, format!("write: {}: {}", path, e)),
        }
    }
}

/// The refusal when `write` was given no content by any route.
///
/// Says the file was left alone, because the failure this replaces did the
/// opposite quietly: `write FILE` with nothing to write truncated FILE to zero
/// bytes and exited 0. An agent reading only the exit code could not tell.
fn missing_content_error(path: &str) -> String {
    format!(
        "write: no content to write — pass it as an operand (write {path} CONTENT), \
         pipe it in, or redirect a file into it; '{path}' is unchanged"
    )
}

/// Render a value as the raw bytes to write. `Bytes` is written verbatim;
/// every other variant uses its lossless string form.
fn value_to_bytes(value: &Value) -> Vec<u8> {
    match value {
        Value::Bytes(b) => b.clone(),
        Value::String(s) => s.clone().into_bytes(),
        Value::Int(i) => i.to_string().into_bytes(),
        Value::Float(f) => f.to_string().into_bytes(),
        Value::Bool(b) => b.to_string().into_bytes(),
        Value::Null => b"null".to_vec(),
        Value::Json(json) => json.to_string().into_bytes(),
    }
}

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

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

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

        let result = Write.execute(args, &mut ctx).await;
        assert!(result.ok());

        // Verify content via backend
        let data = ctx.backend.read(Path::new("/test.txt"), None).await.unwrap();
        assert_eq!(String::from_utf8(data).unwrap(), "hello world");
    }

    #[tokio::test]
    async fn test_write_named() {
        let mut ctx = make_ctx().await;
        let mut args = ToolArgs::new();
        args.positional.push(Value::String("/test.txt".into()));
        args.named.insert("content".to_string(), Value::String("named content".into()));

        let result = Write.execute(args, &mut ctx).await;
        assert!(result.ok());

        let data = ctx.backend.read(Path::new("/test.txt"), None).await.unwrap();
        assert_eq!(String::from_utf8(data).unwrap(), "named content");
    }

    #[tokio::test]
    async fn test_write_nested() {
        let mut ctx = make_ctx().await;
        let mut args = ToolArgs::new();
        args.positional.push(Value::String("/a/b/c.txt".into()));
        args.positional.push(Value::String("nested".into()));

        let result = Write.execute(args, &mut ctx).await;
        assert!(result.ok());

        let data = ctx.backend.read(Path::new("/a/b/c.txt"), None).await.unwrap();
        assert_eq!(String::from_utf8(data).unwrap(), "nested");
    }

    #[tokio::test]
    async fn test_write_no_path() {
        let mut ctx = make_ctx().await;
        let args = ToolArgs::new();

        let result = Write.execute(args, &mut ctx).await;
        assert!(!result.ok());
        assert!(result.err.contains("missing path"));
    }
}