feat: add meta plugin with file and none implementations

src/meta_plugin.rs

@@ -0,0 +1,80 @@
+use anyhow::Result;
+use std::io;
+
+use lazy_static::lazy_static;
+
+extern crate enum_map;
+use enum_map::enum_map;
+use enum_map::{Enum, EnumMap};
+
+pub mod none;
+pub mod program;
+
+use crate::meta_plugin::none::MetaPluginNone;
+use crate::meta_plugin::program::MetaPluginProgram;
+
+use strum::IntoEnumIterator;
+
+#[derive(Debug, Eq, PartialEq, Clone, strum::EnumIter, strum::Display, strum::EnumString, Enum)]
+#[strum(ascii_case_insensitive)]
+pub enum MetaPluginType {
+    File,
+    None,
+}
+
+pub trait MetaPlugin {
+    fn is_supported(&self) -> bool {
+        true
+    }
+    fn create(&self) -> Result<Box<dyn Write>>;
+    fn finalize(&mut self) -> io::Result<String>;
+
+    // Update the meta plugin with new data
+    fn update(&mut self, data: &[u8]);
+}
+
+use std::io::Write;
+
+// Writer that implements Write for the program meta plugin
+struct ProgramWriter {
+    stdin: std::process::ChildStdin,
+}
+
+impl Write for ProgramWriter {
+    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+        self.stdin.write(buf)
+    }
+
+    fn flush(&mut self) -> std::io::Result<()> {
+        self.stdin.flush()
+    }
+}
+
+lazy_static! {
+    pub static ref META_PLUGIN_PROGRAMS: EnumMap<MetaPluginType, Option<MetaPluginProgram>> = enum_map! {
+        MetaPluginType::File => {
+            let program = MetaPluginProgram::new("file", vec!["-bE", "-"]);
+            if program.supported { Some(program) } else { None }
+        }
+        MetaPluginType::None => None
+    };
+}
+
+pub fn get_meta_plugin(meta_plugin_type: MetaPluginType) -> Box<dyn MetaPlugin> {
+    match meta_plugin_type {
+        MetaPluginType::File => Box::new(MetaPluginProgram::new("file", vec!["-bE", "-"])),
+        MetaPluginType::None => Box::new(MetaPluginNone::new()),
+    }
+}
+
+pub fn default_meta_plugin_type() -> MetaPluginType {
+    let mut default = MetaPluginType::None;
+    for meta_plugin_type in MetaPluginType::iter() {
+        let meta_plugin = get_meta_plugin(meta_plugin_type.clone());
+        if meta_plugin.is_supported() {
+            default = meta_plugin_type;
+            break;
+        }
+    }
+    default
+}