feat: refactor and add ip saving

- clean up code to my new (and improved) standards
- print better miette diagnostigs for the error tests
- add an IP saving feature:
    save the last IP that successfully updated the records and usa that
    when restarting the service. This allows seamles upgrades of
    `webnsupdate` without having to manually trigger a DNS update

src/records.rs

@@ -0,0 +1,283 @@
+//! Deal with the DNS records
+
+use std::path::Path;
+
+use miette::{ensure, miette, Context, IntoDiagnostic, LabeledSpan, NamedSource, Result};
+
+/// Loads and verifies the records from a file
+pub fn load(path: &Path) -> Result<()> {
+    let records = std::fs::read_to_string(path)
+        .into_diagnostic()
+        .wrap_err_with(|| format!("failed to read records from {}", path.display()))?;
+
+    verify(&records, path)?;
+
+    Ok(())
+}
+
+/// Load records without verifying them
+pub fn load_no_verify(path: &Path) -> Result<&'static [&'static str]> {
+    let records = std::fs::read_to_string(path)
+        .into_diagnostic()
+        .wrap_err_with(|| format!("failed to read records from {}", path.display()))?;
+
+    if let Err(err) = verify(&records, path) {
+        tracing::error!("Failed to verify records: {err}");
+    }
+
+    // leak memory: we only do this here and it prevents a bunch of allocations
+    let records: &str = records.leak();
+    let records: Box<[&str]> = records.lines().collect();
+
+    Ok(Box::leak(records))
+}
+
+/// Verifies that a list of records is valid
+pub fn verify(data: &str, path: &Path) -> Result<()> {
+    let mut offset = 0usize;
+    for line in data.lines() {
+        validate_line(offset, line).map_err(|err| {
+            err.with_source_code(NamedSource::new(
+                path.display().to_string(),
+                data.to_string(),
+            ))
+        })?;
+
+        offset += line.len() + 1;
+    }
+
+    Ok(())
+}
+
+fn validate_line(offset: usize, line: &str) -> Result<()> {
+    if line.is_empty() {
+        return Ok(());
+    }
+
+    ensure!(
+        line.len() <= 255,
+        miette!(
+            labels = [LabeledSpan::new(
+                Some("this line".to_string()),
+                offset,
+                line.len(),
+            )],
+            help = "fully qualified domain names can be at most 255 characters long",
+            url = "https://en.wikipedia.org/wiki/Fully_qualified_domain_name",
+            "hostname too long ({} octets)",
+            line.len(),
+        )
+    );
+    ensure!(
+        line.ends_with('.'),
+        miette!(
+            labels = [LabeledSpan::new(
+                Some("last character".to_string()),
+                offset + line.len() - 1,
+                1,
+            )],
+            help = "hostname should be a fully qualified domain name (end with a '.')",
+            url = "https://en.wikipedia.org/wiki/Fully_qualified_domain_name",
+            "not a fully qualified domain name"
+        )
+    );
+
+    let mut label_offset = 0usize;
+    for label in line.strip_suffix('.').unwrap_or(line).split('.') {
+        validate_label(offset + label_offset, label)?;
+        label_offset += label.len() + 1;
+    }
+
+    Ok(())
+}
+
+fn validate_label(offset: usize, label: &str) -> Result<()> {
+    ensure!(
+        !label.is_empty(),
+        miette!(
+            labels = [LabeledSpan::new(
+                Some("label".to_string()),
+                offset,
+                label.len(),
+            )],
+            help = "each label should have at least one character",
+            url = "https://en.wikipedia.org/wiki/Fully_qualified_domain_name",
+            "empty label",
+        )
+    );
+    ensure!(
+        label.len() <= 63,
+        miette!(
+            labels = [LabeledSpan::new(
+                Some("label".to_string()),
+                offset,
+                label.len(),
+            )],
+            help = "labels should be at most 63 octets",
+            url = "https://en.wikipedia.org/wiki/Fully_qualified_domain_name",
+            "label too long ({} octets)",
+            label.len(),
+        )
+    );
+
+    for (octet_offset, octet) in label.bytes().enumerate() {
+        validate_octet(offset + octet_offset, octet)?;
+    }
+
+    Ok(())
+}
+
+fn validate_octet(offset: usize, octet: u8) -> Result<()> {
+    let spans = || [LabeledSpan::new(Some("octet".to_string()), offset, 1)];
+    ensure!(
+        octet.is_ascii(),
+        miette!(
+            labels = spans(),
+            help = "we only accept ascii characters",
+            url = "https://en.wikipedia.org/wiki/Hostname#Syntax",
+            "invalid octet: '{}'",
+            octet.escape_ascii(),
+        )
+    );
+
+    ensure!(
+        octet.is_ascii_alphanumeric() || octet == b'-' || octet == b'_',
+        miette!(
+            labels = spans(),
+            help = "hostnames are only allowed to contain characters in [a-zA-Z0-9_-]",
+            url = "https://en.wikipedia.org/wiki/Hostname#Syntax",
+            "invalid octet: '{}'",
+            octet.escape_ascii(),
+        )
+    );
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod test {
+    use crate::records::verify;
+
+    macro_rules! assert_miette_snapshot {
+        ($diag:expr) => {{
+            use std::borrow::Borrow;
+
+            use insta::{with_settings, assert_snapshot};
+            use miette::{GraphicalReportHandler, GraphicalTheme};
+
+            let mut out = String::new();
+            GraphicalReportHandler::new_themed(GraphicalTheme::unicode_nocolor())
+                .with_width(80)
+                .render_report(&mut out, $diag.borrow())
+                .unwrap();
+            with_settings!({
+                description => stringify!($diag)
+            }, {
+                assert_snapshot!(out);
+            });
+        }};
+    }
+
+    #[test]
+    fn valid_records() -> miette::Result<()> {
+        verify(
+            "\
+            example.com.\n\
+            example.org.\n\
+            example.net.\n\
+            subdomain.example.com.\n\
+            ",
+            std::path::Path::new("test_records_valid"),
+        )
+    }
+
+    #[test]
+    fn hostname_too_long() {
+        let err = verify(
+            "\
+            example.com.\n\
+            example.org.\n\
+            example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.example.net.\n\
+            subdomain.example.com.\n\
+            ",
+            std::path::Path::new("test_records_invalid"),
+        )
+        .unwrap_err();
+        assert_miette_snapshot!(err);
+    }
+
+    #[test]
+    fn not_fqd() {
+        let err = verify(
+            "\
+            example.com.\n\
+            example.org.\n\
+            example.net\n\
+            subdomain.example.com.\n\
+            ",
+            std::path::Path::new("test_records_invalid"),
+        )
+        .unwrap_err();
+        assert_miette_snapshot!(err);
+    }
+
+    #[test]
+    fn empty_label() {
+        let err = verify(
+            "\
+            example.com.\n\
+            name..example.org.\n\
+            example.net.\n\
+            subdomain.example.com.\n\
+            ",
+            std::path::Path::new("test_records_invalid"),
+        )
+        .unwrap_err();
+        assert_miette_snapshot!(err);
+    }
+
+    #[test]
+    fn label_too_long() {
+        let err = verify(
+            "\
+            example.com.\n\
+            name.an-entremely-long-label-that-should-not-exist-because-it-goes-against-the-spec.example.org.\n\
+            example.net.\n\
+            subdomain.example.com.\n\
+            ",
+            std::path::Path::new("test_records_invalid"),
+        )
+        .unwrap_err();
+        assert_miette_snapshot!(err);
+    }
+
+    #[test]
+    fn invalid_ascii() {
+        let err = verify(
+            "\
+            example.com.\n\
+            name.this-is-not-aßcii.example.org.\n\
+            example.net.\n\
+            subdomain.example.com.\n\
+            ",
+            std::path::Path::new("test_records_invalid"),
+        )
+        .unwrap_err();
+        assert_miette_snapshot!(err);
+    }
+
+    #[test]
+    fn invalid_octet() {
+        let err = verify(
+            "\
+            example.com.\n\
+            name.this-character:-is-not-allowed.example.org.\n\
+            example.net.\n\
+            subdomain.example.com.\n\
+            ",
+            std::path::Path::new("test_records_invalid"),
+        )
+        .unwrap_err();
+        assert_miette_snapshot!(err);
+    }
+}