feat: oci compliance work (#85)

* chore: rework oci crate to be more composable

* feat: image pull is now internally explicit

* feat: utilize vfs for assembling oci images

* feat: rework oci to preserve permissions via a vfs

crates/oci/src/packer/backend.rs

@@ -0,0 +1,201 @@
+use std::{path::Path, process::Stdio, sync::Arc};
+
+use super::OciPackedFormat;
+use crate::{
+    progress::{OciBoundProgress, OciProgressPhase},
+    vfs::VfsTree,
+};
+use anyhow::{anyhow, Result};
+use log::warn;
+use tokio::{pin, process::Command, select};
+
+#[derive(Debug, Clone, Copy)]
+pub enum OciPackerBackendType {
+    MkSquashfs,
+    MkfsErofs,
+}
+
+impl OciPackerBackendType {
+    pub fn format(&self) -> OciPackedFormat {
+        match self {
+            OciPackerBackendType::MkSquashfs => OciPackedFormat::Squashfs,
+            OciPackerBackendType::MkfsErofs => OciPackedFormat::Erofs,
+        }
+    }
+
+    pub fn create(&self) -> Box<dyn OciPackerBackend> {
+        match self {
+            OciPackerBackendType::MkSquashfs => {
+                Box::new(OciPackerMkSquashfs {}) as Box<dyn OciPackerBackend>
+            }
+            OciPackerBackendType::MkfsErofs => {
+                Box::new(OciPackerMkfsErofs {}) as Box<dyn OciPackerBackend>
+            }
+        }
+    }
+}
+
+#[async_trait::async_trait]
+pub trait OciPackerBackend: Send + Sync {
+    async fn pack(&self, progress: OciBoundProgress, vfs: Arc<VfsTree>, file: &Path) -> Result<()>;
+}
+
+pub struct OciPackerMkSquashfs {}
+
+#[async_trait::async_trait]
+impl OciPackerBackend for OciPackerMkSquashfs {
+    async fn pack(&self, progress: OciBoundProgress, vfs: Arc<VfsTree>, file: &Path) -> Result<()> {
+        progress
+            .update(|progress| {
+                progress.phase = OciProgressPhase::Packing;
+                progress.total = 1;
+                progress.value = 0;
+            })
+            .await;
+
+        let mut child = Command::new("mksquashfs")
+            .arg("-")
+            .arg(file)
+            .arg("-comp")
+            .arg("gzip")
+            .arg("-tar")
+            .stdin(Stdio::piped())
+            .stderr(Stdio::null())
+            .stdout(Stdio::null())
+            .spawn()?;
+        let stdin = child
+            .stdin
+            .take()
+            .ok_or(anyhow!("unable to acquire stdin stream"))?;
+        let mut writer = Some(tokio::task::spawn(async move {
+            if let Err(error) = vfs.write_to_tar(stdin).await {
+                warn!("failed to write tar: {}", error);
+                return Err(error);
+            }
+            Ok(())
+        }));
+        let wait = child.wait();
+        pin!(wait);
+        let status_result = loop {
+            if let Some(inner) = writer.as_mut() {
+                select! {
+                    x = inner => {
+                        writer = None;
+                        match x {
+                            Ok(_) => {},
+                            Err(error) => {
+                                return Err(error.into());
+                            }
+                        }
+                    },
+                    status = &mut wait => {
+                        break status;
+                    }
+                };
+            } else {
+                select! {
+                    status = &mut wait => {
+                        break status;
+                    }
+                };
+            }
+        };
+        if let Some(writer) = writer {
+            writer.await??;
+        }
+        let status = status_result?;
+        if !status.success() {
+            Err(anyhow!(
+                "mksquashfs failed with exit code: {}",
+                status.code().unwrap()
+            ))
+        } else {
+            progress
+                .update(|progress| {
+                    progress.phase = OciProgressPhase::Packing;
+                    progress.total = 1;
+                    progress.value = 1;
+                })
+                .await;
+            Ok(())
+        }
+    }
+}
+
+pub struct OciPackerMkfsErofs {}
+
+#[async_trait::async_trait]
+impl OciPackerBackend for OciPackerMkfsErofs {
+    async fn pack(&self, progress: OciBoundProgress, vfs: Arc<VfsTree>, path: &Path) -> Result<()> {
+        progress
+            .update(|progress| {
+                progress.phase = OciProgressPhase::Packing;
+                progress.total = 1;
+                progress.value = 0;
+            })
+            .await;
+
+        let mut child = Command::new("mkfs.erofs")
+            .arg("-L")
+            .arg("root")
+            .arg("--tar=-")
+            .arg(path)
+            .stdin(Stdio::piped())
+            .stderr(Stdio::null())
+            .stdout(Stdio::null())
+            .spawn()?;
+        let stdin = child
+            .stdin
+            .take()
+            .ok_or(anyhow!("unable to acquire stdin stream"))?;
+        let mut writer = Some(tokio::task::spawn(
+            async move { vfs.write_to_tar(stdin).await },
+        ));
+        let wait = child.wait();
+        pin!(wait);
+        let status_result = loop {
+            if let Some(inner) = writer.as_mut() {
+                select! {
+                    x = inner => {
+                        match x {
+                            Ok(_) => {
+                                writer = None;
+                            },
+                            Err(error) => {
+                                return Err(error.into());
+                            }
+                        }
+                    },
+                    status = &mut wait => {
+                        break status;
+                    }
+                };
+            } else {
+                select! {
+                    status = &mut wait => {
+                        break status;
+                    }
+                };
+            }
+        };
+        if let Some(writer) = writer {
+            writer.await??;
+        }
+        let status = status_result?;
+        if !status.success() {
+            Err(anyhow!(
+                "mkfs.erofs failed with exit code: {}",
+                status.code().unwrap()
+            ))
+        } else {
+            progress
+                .update(|progress| {
+                    progress.phase = OciProgressPhase::Packing;
+                    progress.total = 1;
+                    progress.value = 1;
+                })
+                .await;
+            Ok(())
+        }
+    }
+}