Rewrite in Rust (#3)

Just what the world needs, another silly Rust re-write! But it was a good exercise in learning.

There's a lot of messy things, which is why this is 0.2.0-pre.1. Going to make some cleaning passes after landing this.

src/config.rs

@@ -0,0 +1,77 @@
+use anyhow::Context;
+use serde::{Deserialize, Serialize};
+use std::fs;
+use std::path::PathBuf;
+
+#[derive(Serialize, Deserialize, Debug, PartialEq)]
+#[serde(default)]
+pub struct Config {
+    /// Tuple of how big thumbnails should be - (width, height)
+    pub thumbnail_size: (u32, u32),
+    /// Tuple of how big thumbnails should be - (width, height)
+    pub view_size: (u32, u32),
+    /// Directory inside the album that the site should be output to
+    pub output_dir: PathBuf,
+}
+
+impl Config {
+    pub fn from_album(path: PathBuf) -> anyhow::Result<Config> {
+        let config_path = path.join("photojawn.conf.yml");
+        let content = fs::read(&config_path).with_context(|| {
+            format!(
+                "Failed to read config from {}. Is this an album directory?",
+                config_path.display(),
+            )
+        })?;
+        let cfg = serde_yml::from_slice(&content)
+            .with_context(|| format!("Failed to parse config from {}", config_path.display()))?;
+        Ok(cfg)
+    }
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Self {
+            thumbnail_size: (256, 256),
+            view_size: (1024, 768),
+            output_dir: PathBuf::from("site"),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::skel::make_skeleton;
+    use mktemp::Temp;
+
+    #[test]
+    fn test_default() {
+        let c = Config::default();
+        assert_eq!(c.thumbnail_size, (256, 256));
+        assert_eq!(c.output_dir, PathBuf::from("site"));
+    }
+
+    #[test]
+    fn from_yaml() {
+        // Empty YAML gives full default values
+        let default_cfg = Config::default();
+        let cfg: Config = serde_yml::from_str("").unwrap();
+        assert_eq!(cfg, default_cfg);
+
+        // Default values for any unspecified fields
+        let cfg: Config = serde_yml::from_str("thumbnail_size: [1, 1]").unwrap();
+        assert_ne!(cfg, default_cfg);
+        assert_eq!(cfg.thumbnail_size, (1, 1));
+        assert_eq!(cfg.view_size, default_cfg.view_size);
+    }
+
+    #[test]
+    fn from_base_album() {
+        let tmpdir = Temp::new_dir().unwrap();
+        make_skeleton(&tmpdir).unwrap();
+
+        let cfg = Config::from_album(tmpdir.to_path_buf()).unwrap();
+        assert_eq!(cfg, Config::default());
+    }
+}