//! APT sources.list management
//! Provides a simple structure for managing APT repository sources
//!
//! Entries carry enough information (kind, signed-by, trusted, enabled) to
//! be written back without loss, and remember the file they were loaded
//! from ([`SourceEntry::origin`]) so that saving writes each entry back to
//! its own file, in that file's own format.
use crate::context::{self, Context};
use crate::debian::control::{Paragraph, parse_paragraphs, write_paragraph};
use std::error::Error;
use std::path::{Path, PathBuf};
use std::sync::Arc;

/// Sources file owned by pkh, holding entries added by pkh (e.g. PPAs).
///
/// New entries never end up in distro-managed files.
const PKH_ADDED_PATH: &str = "/etc/apt/sources.list.d/pkh-added.list";

/// Suffix appended to an origin file path to build its backup path
const BACKUP_SUFFIX: &str = ".pkh-backup";

/// Kind of packages provided by a source entry
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum SourceKind {
    /// Binary packages ('deb')
    Deb,
    /// Source packages ('deb-src')
    DebSrc,
}

impl SourceKind {
    /// Token used in legacy lines and deb822 'Types' fields
    pub fn as_str(self) -> &'static str {
        match self {
            SourceKind::Deb => "deb",
            SourceKind::DebSrc => "deb-src",
        }
    }

    /// Parse a type token ('deb' or 'deb-src')
    fn parse(token: &str) -> Option<Self> {
        match token {
            "deb" => Some(SourceKind::Deb),
            "deb-src" => Some(SourceKind::DebSrc),
            _ => None,
        }
    }
}

/// On-disk format of a sources file
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum SourceFormat {
    /// Legacy one-line-per-entry format (sources.list, *.list)
    Legacy,
    /// deb822 format (*.sources)
    Deb822,
}

/// File a source entry was loaded from
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct SourceOrigin {
    /// Path of the origin file, inside the context
    pub path: PathBuf,
    /// Format of the origin file
    pub format: SourceFormat,
}

/// Represents a single source entry in sources.list
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct SourceEntry {
    /// Is the source enabled?
    pub enabled: bool,
    /// Kind of packages provided by the source (binary or source)
    pub kind: SourceKind,
    /// Source components (universe, main, contrib)
    pub components: Vec<String>,
    /// Source architectures (amd64, riscv64, arm64)
    pub architectures: Vec<String>,
    /// Keyring the repository is signed with ('signed-by' option)
    pub signed_by: Option<String>,
    /// Explicit trust flag ('trusted' option), when set
    pub trusted: Option<bool>,
    /// Source URI
    pub uri: String,
    /// Source suites (series-pocket)
    pub suite: Vec<String>,
    /// File and format the entry was loaded from
    ///
    /// Entries without an origin are new (e.g. repositories added by pkh);
    /// they are saved to the pkh-owned added-sources file.
    pub origin: Option<SourceOrigin>,
}

impl SourceEntry {
    /// Build entries from a single deb822 stanza
    ///
    /// A stanza declaring several types ('Types: deb deb-src') yields one
    /// entry per type.
    fn from_deb822_stanza(p: &Paragraph) -> Vec<Self> {
        // apt defaults 'Types' to 'deb' when the field is absent
        let mut kinds: Vec<SourceKind> = p
            .get("Types")
            .unwrap_or("deb")
            .split_whitespace()
            .filter_map(SourceKind::parse)
            .collect();
        if kinds.is_empty() {
            kinds.push(SourceKind::Deb);
        }

        let enabled = p
            .get("Enabled")
            .map(|v| {
                let v = v.trim();
                !v.eq_ignore_ascii_case("no") && !v.eq_ignore_ascii_case("false")
            })
            .unwrap_or(true);
        let signed_by = p
            .get("Signed-By")
            .map(str::trim)
            .filter(|v| !v.is_empty())
            .map(str::to_string);
        let trusted = p
            .get("Trusted")
            .map(|v| v.trim().eq_ignore_ascii_case("yes"));
        let uri = p.get("URIs").unwrap_or("").trim().to_string();
        if uri.is_empty() {
            return Vec::new();
        }
        let suite: Vec<String> = p
            .get("Suites")
            .unwrap_or("")
            .split_whitespace()
            .map(|s| s.to_string())
            .collect();
        let components: Vec<String> = p
            .get("Components")
            .unwrap_or("")
            .split_whitespace()
            .map(|s| s.to_string())
            .collect();
        let architectures: Vec<String> = p
            .get("Architectures")
            .unwrap_or("")
            .split_whitespace()
            .map(|s| s.to_string())
            .collect();

        kinds
            .into_iter()
            .map(|kind| SourceEntry {
                enabled,
                kind,
                components: components.clone(),
                architectures: architectures.clone(),
                signed_by: signed_by.clone(),
                trusted,
                uri: uri.clone(),
                suite: suite.clone(),
                origin: None,
            })
            .collect()
    }

    /// Parse a line describing a legacy source entry
    pub fn from_legacy(data: &str) -> Option<Self> {
        let raw = data.lines().next()?.trim();

        if raw.is_empty() {
            return None;
        }

        // Entries commented out with '#' are disabled, not deleted
        let (enabled, line) = match raw.strip_prefix('#') {
            Some(rest) => (false, rest.trim_start()),
            None => (true, raw),
        };

        // Parse legacy deb line format:
        // deb [arch=... signed-by=... trusted=...] uri suite [components...]

        // Extract bracket parameters first
        let mut architectures = Vec::new();
        let mut signed_by = None;
        let mut trusted = None;
        let mut line_without_brackets = line.to_string();

        // Find and process bracket parameters
        if let Some(start_bracket) = line.find('[')
            && let Some(end_bracket) = line.find(']')
        {
            let bracket_content = &line[start_bracket + 1..end_bracket];

            // Parse parameters inside brackets
            for param in bracket_content.split_whitespace() {
                if let Some(values) = param.strip_prefix("arch=") {
                    architectures = values.split(',').map(|s| s.trim().to_string()).collect();
                } else if let Some(keyring) = param.strip_prefix("signed-by=") {
                    signed_by = Some(keyring.trim_matches('"').to_string());
                } else if let Some(flag) = param.strip_prefix("trusted=") {
                    trusted = Some(flag.eq_ignore_ascii_case("yes") || flag == "1");
                }
            }

            // Remove the bracket section from the line
            line_without_brackets = line[..start_bracket].to_string() + &line[end_bracket + 1..];
        }

        // Trim and split the remaining line
        let line_without_brackets = line_without_brackets.trim();
        let parts: Vec<&str> = line_without_brackets.split_whitespace().collect();

        // We need at least: type, uri, suite
        if parts.len() < 3 {
            return None;
        }
        let kind = SourceKind::parse(parts[0])?;

        let uri = parts[1].to_string();
        let suite = vec![parts[2].to_string()];
        let components: Vec<String> = parts[3..].iter().map(|&s| s.to_string()).collect();

        Some(SourceEntry {
            enabled,
            kind,
            components,
            architectures,
            signed_by,
            trusted,
            uri,
            suite,
            origin: None,
        })
    }

    /// Convert this source entry to legacy format
    ///
    /// Entries holding several suites are rendered as one line per suite.
    /// Disabled entries are commented out.
    pub fn to_legacy(&self) -> String {
        let mut result = String::new();

        // Legacy entries contain one suite per line
        for suite in &self.suite {
            if !self.enabled {
                result.push_str("# ");
            }
            result.push_str(self.kind.as_str());

            // Bracket options: architectures, signing keyring and trust
            let mut options = Vec::new();
            if !self.architectures.is_empty() {
                options.push(format!("arch={}", self.architectures.join(",")));
            }
            if let Some(keyring) = &self.signed_by {
                if keyring.contains(char::is_whitespace) {
                    options.push(format!("signed-by=\"{keyring}\""));
                } else {
                    options.push(format!("signed-by={keyring}"));
                }
            }
            if let Some(trusted) = self.trusted {
                options.push(format!("trusted={}", if trusted { "yes" } else { "no" }));
            }
            if !options.is_empty() {
                result.push_str(" [");
                result.push_str(&options.join(" "));
                result.push(']');
            }

            // Add URI and suite
            result.push(' ');
            result.push_str(&self.uri);
            result.push(' ');
            result.push_str(suite);

            // Add components
            if !self.components.is_empty() {
                result.push(' ');
                result.push_str(&self.components.join(" "));
            }

            result.push('\n');
        }

        result
    }

    /// Convert this source entry to a deb822 stanza (with a trailing newline)
    pub fn to_deb822(&self) -> String {
        let mut stanza = Paragraph::new();
        stanza.set("Types", self.kind.as_str());
        stanza.set("URIs", &self.uri);
        stanza.set("Suites", &self.suite.join(" "));
        stanza.set("Components", &self.components.join(" "));
        if let Some(keyring) = &self.signed_by {
            stanza.set("Signed-By", keyring);
        }
        if !self.architectures.is_empty() {
            stanza.set("Architectures", &self.architectures.join(" "));
        }
        if let Some(trusted) = self.trusted {
            stanza.set("Trusted", if trusted { "yes" } else { "no" });
        }
        if !self.enabled {
            stanza.set("Enabled", "no");
        }
        write_paragraph(&stanza)
    }
}

/// Parse a 'source list' string in deb822 format into a SourceEntry vector
///
/// A stanza declaring several types ('Types: deb deb-src') yields one entry
/// per type.
pub fn parse_deb822(data: &str) -> Vec<SourceEntry> {
    parse_paragraphs(data)
        .iter()
        .flat_map(SourceEntry::from_deb822_stanza)
        .collect()
}

/// Parse a 'source list' string in legacy format into a SourceEntry vector
pub fn parse_legacy(data: &str) -> Vec<SourceEntry> {
    data.split('\n')
        .flat_map(SourceEntry::from_legacy)
        .collect()
}

/// Load sources from context (or current context by default)
///
/// Reads the deb822 distro sources (ubuntu.sources or debian.sources), the
/// legacy '/etc/apt/sources.list' and the pkh-owned added-sources file when
/// they exist. Every entry remembers the file and format it came from.
pub fn load(ctx: Option<Arc<Context>>) -> Result<Vec<SourceEntry>, Box<dyn Error>> {
    let mut sources = Vec::new();
    let ctx = ctx.unwrap_or_else(context::current);

    // Try DEB822 format first (Ubuntu 24.04+ and Debian Trixie+)
    load_file(
        &ctx,
        "/etc/apt/sources.list.d/ubuntu.sources",
        SourceFormat::Deb822,
        &mut sources,
    )?;
    load_file(
        &ctx,
        "/etc/apt/sources.list.d/debian.sources",
        SourceFormat::Deb822,
        &mut sources,
    )?;

    // Fall back to legacy format
    load_file(
        &ctx,
        "/etc/apt/sources.list",
        SourceFormat::Legacy,
        &mut sources,
    )?;

    // Entries added by a previous pkh run
    load_file(&ctx, PKH_ADDED_PATH, SourceFormat::Legacy, &mut sources)?;

    Ok(sources)
}

/// Save sources back to the context
///
/// Each entry is written back to the file it was loaded from
/// ([`SourceEntry::origin`]), in that file's format. Entries without an
/// origin (e.g. repositories added by pkh) go to the pkh-owned
/// added-sources file in legacy format, never to distro-managed files.
///
/// Files whose rendered content is byte-identical to their current content
/// are left untouched; otherwise a '<path>.pkh-backup' copy is created once
/// before the first overwrite.
pub fn save(ctx: Option<Arc<Context>>, sources: Vec<SourceEntry>) -> Result<(), Box<dyn Error>> {
    let ctx = ctx.unwrap_or_else(context::current);

    for (path, _format, content) in plan_writes(&sources) {
        let original = if ctx.exists(&path)? {
            Some(ctx.read_file(&path)?)
        } else {
            None
        };
        if original.as_deref() == Some(content.as_str()) {
            // Nothing changed: leave the file untouched
            continue;
        }

        // One-time backup before overwriting an existing file
        if original.is_some() {
            let backup = backup_path(&path);
            if !ctx.exists(&backup)? {
                ctx.copy_path(&path, &backup)?;
            }
        }

        ctx.write_file(&path, &content)?;
    }

    Ok(())
}

/// Load entries from one sources file, if it exists, tagging them with
/// their origin
fn load_file(
    ctx: &Context,
    path: &str,
    format: SourceFormat,
    out: &mut Vec<SourceEntry>,
) -> Result<(), Box<dyn Error>> {
    let path = PathBuf::from(path);
    if !ctx.exists(&path)? {
        return Ok(());
    }

    let content = ctx.read_file(&path)?;
    let mut entries = match format {
        SourceFormat::Deb822 => parse_deb822(&content),
        SourceFormat::Legacy => parse_legacy(&content),
    };
    for entry in &mut entries {
        entry.origin = Some(SourceOrigin {
            path: path.clone(),
            format,
        });
    }
    out.append(&mut entries);
    Ok(())
}

/// Compute the writes needed to persist entries: one
/// (path, format, content) triple per destination file, entries kept in order
///
/// Entries without an origin are routed to the pkh-owned added-sources file.
fn plan_writes(sources: &[SourceEntry]) -> Vec<(PathBuf, SourceFormat, String)> {
    let mut plan: Vec<(PathBuf, SourceFormat, Vec<&SourceEntry>)> = Vec::new();
    for entry in sources {
        let (path, format) = match &entry.origin {
            Some(origin) => (origin.path.clone(), origin.format),
            None => (PathBuf::from(PKH_ADDED_PATH), SourceFormat::Legacy),
        };
        if let Some((_, _, group)) = plan.iter_mut().find(|(p, _, _)| *p == path) {
            group.push(entry);
        } else {
            plan.push((path, format, vec![entry]));
        }
    }

    plan.into_iter()
        .map(|(path, format, entries)| {
            let content = match format {
                // Legacy entries end with '\n': plain concatenation, no
                // blank lines in between
                SourceFormat::Legacy => entries.iter().map(|e| e.to_legacy()).collect(),
                // deb822 stanzas end with '\n': a '\n' join gives one blank
                // line between stanzas
                SourceFormat::Deb822 => entries
                    .iter()
                    .map(|e| e.to_deb822())
                    .collect::<Vec<_>>()
                    .join("\n"),
            };
            (path, format, content)
        })
        .collect()
}

/// Backup path for a sources file ('<path>.pkh-backup')
fn backup_path(path: &Path) -> PathBuf {
    let mut with_suffix = path.as_os_str().to_os_string();
    with_suffix.push(BACKUP_SUFFIX);
    PathBuf::from(with_suffix)
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::context::ContextConfig;

    #[tokio::test]
    async fn test_parse_deb822() {
        let deb822 = "\
        Types: deb\n\
        URIs: http://fr.archive.ubuntu.com/ubuntu/\n\
        Suites: questing questing-updates questing-backports\n\
        Components: main restricted universe multiverse\n\
        Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg\n\
        Architectures: amd64\n\
        \n\
        Types: deb\n\
        URIs: http://security.ubuntu.com/ubuntu/\n\
        Suites: questing-security\n\
        Components: main restricted universe multiverse\n\
        Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg\n\
        Architectures: amd64\n\
        \n\
        Types: deb\n\
        URIs: http://ports.ubuntu.com/ubuntu-ports/\n\
        Suites: questing questing-updates questing-backports\n\
        Components: main restricted universe multiverse\n\
        Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg\n\
        Architectures: riscv64\n\
        ";

        let sources = parse_deb822(deb822);
        assert_eq!(sources.len(), 3);
        assert_eq!(sources[0].uri, "http://fr.archive.ubuntu.com/ubuntu/");
        assert_eq!(sources[0].architectures, vec!["amd64"]);
        assert_eq!(
            sources[0].suite,
            vec!["questing", "questing-updates", "questing-backports"]
        );
        assert_eq!(
            sources[0].components,
            vec!["main", "restricted", "universe", "multiverse"]
        );
        assert_eq!(sources[1].uri, "http://security.ubuntu.com/ubuntu/");
        assert_eq!(sources[1].architectures, vec!["amd64"]);
        assert_eq!(sources[1].suite, vec!["questing-security"]);
        assert_eq!(
            sources[1].components,
            vec!["main", "restricted", "universe", "multiverse"]
        );
        assert_eq!(sources[2].uri, "http://ports.ubuntu.com/ubuntu-ports/");
        assert_eq!(sources[2].architectures.len(), 1);
        assert_eq!(sources[2].architectures, vec!["riscv64"]);
        assert_eq!(
            sources[2].suite,
            vec!["questing", "questing-updates", "questing-backports"]
        );
        assert_eq!(
            sources[2].components,
            vec!["main", "restricted", "universe", "multiverse"]
        );
    }

    #[tokio::test]
    async fn test_parse_legacy() {
        let legacy = "\
        deb [signed-by=\"/usr/share/keyrings/ubuntu-archive-keyring.gpg\" arch=amd64] http://archive.ubuntu.com/ubuntu resolute main universe\n\
        deb [arch=amd64,i386 signed-by=\"/usr/share/keyrings/ubuntu-archive-keyring.gpg\"] http://archive.ubuntu.com/ubuntu resolute-updates main\n\
        deb [signed-by=\"/usr/share/keyrings/ubuntu-archive-keyring.gpg\"] http://security.ubuntu.com/ubuntu resolute-security main\n\
        ";

        let sources = parse_legacy(legacy);
        assert_eq!(sources.len(), 3);
        assert_eq!(sources[0].uri, "http://archive.ubuntu.com/ubuntu");
        assert_eq!(sources[0].suite, vec!["resolute"]);
        assert_eq!(sources[0].components, vec!["main", "universe"]);
        assert_eq!(sources[0].architectures, vec!["amd64"]);
        assert_eq!(sources[1].uri, "http://archive.ubuntu.com/ubuntu");
        assert_eq!(sources[1].suite, vec!["resolute-updates"]);
        assert_eq!(sources[1].components, vec!["main"]);
        assert_eq!(sources[1].architectures, vec!["amd64", "i386"]);
        assert_eq!(sources[2].uri, "http://security.ubuntu.com/ubuntu");
        assert_eq!(sources[2].suite, vec!["resolute-security"]);
        assert_eq!(sources[2].components, vec!["main"]);
    }

    /// Legacy round-trip: kind, signed-by, trusted and arch are preserved,
    /// and rendering introduces no blank lines
    #[test]
    fn legacy_roundtrip_preserves_options() {
        let input = "\
            deb [arch=amd64 signed-by=/k.gpg] http://x noble main\n\
            deb-src http://x noble main\n\
            deb [trusted=yes] http://x noble universe\n\
            # deb [arch=i386] http://x noble main\n";

        let sources = parse_legacy(input);
        assert_eq!(sources.len(), 4);
        assert_eq!(sources[0].kind, SourceKind::Deb);
        assert_eq!(sources[0].signed_by.as_deref(), Some("/k.gpg"));
        assert_eq!(sources[0].architectures, vec!["amd64"]);
        assert_eq!(sources[1].kind, SourceKind::DebSrc);
        assert_eq!(sources[2].trusted, Some(true));
        assert!(!sources[3].enabled);

        // Render as a legacy file through the save planning path
        let origin = SourceOrigin {
            path: PathBuf::from("/etc/apt/sources.list"),
            format: SourceFormat::Legacy,
        };
        let mut sources = sources;
        for entry in &mut sources {
            entry.origin = Some(origin.clone());
        }
        let plan = plan_writes(&sources);
        assert_eq!(plan.len(), 1);
        let rendered = &plan[0].2;

        // Rendering is faithful: byte-identical and without blank lines
        assert_eq!(rendered, input);
        assert!(!rendered.contains("\n\n"));

        let reparsed = parse_legacy(rendered);
        assert_eq!(reparsed, parse_legacy(input));
    }

    /// deb822 round-trip: multiple types are split into one entry per type,
    /// Signed-By and Enabled are preserved
    #[test]
    fn deb822_roundtrip_preserves_types_and_options() {
        let input = "\
            Types: deb deb-src\n\
            URIs: http://archive.ubuntu.com/ubuntu\n\
            Suites: noble\n\
            Components: main\n\
            Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg\n\
            Enabled: false\n\
            \n\
            Types: deb\n\
            URIs: http://archive.ubuntu.com/ubuntu\n\
            Suites: noble-updates\n\
            Components: main universe\n";

        let sources = parse_deb822(input);
        // The first stanza declares two types: one entry per type
        assert_eq!(sources.len(), 3);
        assert_eq!(sources[0].kind, SourceKind::Deb);
        assert_eq!(sources[1].kind, SourceKind::DebSrc);
        assert_eq!(sources[2].kind, SourceKind::Deb);
        assert!(!sources[0].enabled);
        assert!(!sources[1].enabled);
        assert!(sources[2].enabled);
        assert_eq!(
            sources[0].signed_by.as_deref(),
            Some("/usr/share/keyrings/ubuntu-archive-keyring.gpg")
        );
        assert_eq!(sources[1].signed_by, sources[0].signed_by);
        assert_eq!(sources[2].signed_by, None);

        // Render as a deb822 file through the save planning path
        let mut sources = sources;
        for entry in &mut sources {
            entry.origin = Some(SourceOrigin {
                path: PathBuf::from("/etc/apt/sources.list.d/ubuntu.sources"),
                format: SourceFormat::Deb822,
            });
        }
        let plan = plan_writes(&sources);
        assert_eq!(plan.len(), 1);
        let rendered = &plan[0].2;

        let reparsed = parse_deb822(rendered);
        // Parse/render round-trip preserves the model (origin excepted)
        assert_eq!(reparsed, parse_deb822(input));
        assert_eq!(reparsed[0].kind, SourceKind::Deb);
        assert_eq!(reparsed[1].kind, SourceKind::DebSrc);
        assert_eq!(reparsed[2].kind, SourceKind::Deb);
        assert!(!reparsed[0].enabled);
        assert!(!reparsed[1].enabled);
        assert!(reparsed[2].enabled);
        assert_eq!(
            reparsed[0].signed_by.as_deref(),
            Some("/usr/share/keyrings/ubuntu-archive-keyring.gpg")
        );
        // 'Enabled' is only emitted for disabled entries
        assert_eq!(rendered.matches("Enabled: no").count(), 2);
    }

    /// Entries are routed to their origin file in its own format, and new
    /// entries (no origin) go to the pkh-owned added-sources file
    #[test]
    fn plan_writes_routes_by_origin() {
        let origin_a = SourceOrigin {
            path: PathBuf::from("/etc/apt/sources.list.d/ubuntu.sources"),
            format: SourceFormat::Deb822,
        };

        let mut sources = parse_deb822(
            "Types: deb\nURIs: http://archive.ubuntu.com/ubuntu\nSuites: noble\nComponents: main\n",
        );
        sources[0].origin = Some(origin_a.clone());

        // Modify the origin-A entry and add a brand new (PPA) entry
        sources[0].components.push("universe".to_string());
        sources.push(SourceEntry {
            enabled: true,
            kind: SourceKind::Deb,
            components: vec!["main".to_string()],
            architectures: vec![],
            signed_by: None,
            trusted: None,
            uri: "http://ppa.example.org/user/ppa/ubuntu".to_string(),
            suite: vec!["noble".to_string()],
            origin: None,
        });

        let plan = plan_writes(&sources);
        assert_eq!(plan.len(), 2);

        assert_eq!(plan[0].0, origin_a.path);
        assert_eq!(plan[0].1, SourceFormat::Deb822);
        assert!(plan[0].2.starts_with("Types: deb\n"));
        assert!(plan[0].2.contains("main universe"));

        assert_eq!(
            plan[1].0,
            PathBuf::from("/etc/apt/sources.list.d/pkh-added.list")
        );
        assert_eq!(plan[1].1, SourceFormat::Legacy);
        assert!(plan[1].2.starts_with("deb http://ppa.example.org/"));
    }

    /// save() leaves unchanged files untouched, and backs up existing files
    /// once before overwriting them; the backup also works for the
    /// pkh-owned added-sources file
    #[test]
    fn save_skips_unchanged_and_backs_up() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("ubuntu.sources");
        std::fs::write(
            &path,
            "Types: deb\nURIs: http://a\nSuites: noble\nComponents: main\n",
        )
        .unwrap();
        let ctx = Arc::new(Context::new(ContextConfig::Local).unwrap());

        let origin = SourceOrigin {
            path: path.clone(),
            format: SourceFormat::Deb822,
        };
        let mut entries =
            parse_deb822("Types: deb\nURIs: http://a\nSuites: noble\nComponents: main\n");
        entries[0].origin = Some(origin.clone());

        // Unchanged content: no write, no backup
        save(Some(ctx.clone()), entries.clone()).unwrap();
        assert_eq!(
            std::fs::read_to_string(&path).unwrap(),
            "Types: deb\nURIs: http://a\nSuites: noble\nComponents: main\n"
        );
        assert!(!backup_path(&path).exists());

        // Modified content: backup created, file rewritten in its own format
        entries[0].components.push("universe".to_string());
        save(Some(ctx.clone()), entries).unwrap();
        assert_eq!(
            std::fs::read_to_string(backup_path(&path)).unwrap(),
            "Types: deb\nURIs: http://a\nSuites: noble\nComponents: main\n"
        );
        assert_eq!(
            std::fs::read_to_string(&path).unwrap(),
            "Types: deb\nURIs: http://a\nSuites: noble\nComponents: main universe\n"
        );

        // A second save does not overwrite the first backup
        let mut entries =
            parse_deb822("Types: deb\nURIs: http://a\nSuites: noble\nComponents: main universe\n");
        entries[0].origin = Some(origin);
        entries[0].components.push("restricted".to_string());
        save(Some(ctx.clone()), entries).unwrap();
        assert_eq!(
            std::fs::read_to_string(backup_path(&path)).unwrap(),
            "Types: deb\nURIs: http://a\nSuites: noble\nComponents: main\n"
        );
        assert_eq!(
            std::fs::read_to_string(&path).unwrap(),
            "Types: deb\nURIs: http://a\nSuites: noble\nComponents: main universe restricted\n"
        );
    }
}