//! Native `.changes` generation (Format 1.8), mirroring `dpkg-genchanges`
//! for the artifact aggregation part: checksums, per-file sections and
//! priorities, changelog-derived fields.

use std::path::Path;

use crate::debian::checksums::FileChecksums;
use crate::debian::control::{Paragraph, write_paragraph};
use crate::debian::files::FilesList;

/// Everything needed to render a `.changes` file.
#[derive(Debug, Clone)]
pub struct ChangesInput {
    /// `Date` field: the changelog entry date (verbatim trailer date).
    pub date: String,
    /// `Source` field, including the ` (sourceversion)` suffix for binNMUs.
    pub source: String,
    /// Sorted binary package names with artifacts (empty for source-only).
    pub binaries: Vec<String>,
    /// Active build profiles (`Built-For-Profiles`); omitted when empty.
    pub built_for_profiles: Vec<String>,
    /// `Architecture` field value in encounter order (e.g. `source`,
    /// `amd64 all`, ...).
    pub architecture: String,
    /// Full version.
    pub version: String,
    /// Distribution(s).
    pub distribution: String,
    /// Urgency.
    pub urgency: String,
    /// `Maintainer` from the control source stanza.
    pub maintainer: Option<String>,
    /// `Changed-By` from the changelog maintainer.
    pub changed_by: Option<String>,
    /// Formatted per-package description lines (empty for source-only).
    pub descriptions: Vec<String>,
    /// Bug numbers collected from the changelog (`Closes` field), if any.
    pub closes: Option<String>,
    /// Rendered `Changes` field value from the changelog entry.
    pub changes_field: String,
    /// Computed artifact checksums (dsc, tarballs, debs, buildinfo).
    pub checksums: FileChecksums,
    /// Registry providing section/priority per file.
    pub files_list: FilesList,
}

/// Wrap an overly long single-line field value (> 980 characters) over
/// multiple lines at spaces, like dpkg does for `Binary`.
fn wrap_long(value: &str) -> String {
    if value.len() <= 980 {
        return value.to_string();
    }
    let mut out = String::with_capacity(value.len() + 8);
    let mut line_len = 0usize;
    for (i, word) in value.split(' ').enumerate() {
        if i > 0 {
            if line_len + 1 + word.len() > 980 {
                out.push('\n');
                line_len = 0;
            } else {
                out.push(' ');
                line_len += 1;
            }
        }
        out.push_str(word);
        line_len += word.len();
    }
    out
}

/// Format one `Description` line: `%-10s - %-.65s` plus a ` (type)` suffix
/// for non-deb package types, matching `format_desc()` in dpkg-genchanges.
pub fn format_description(package: &str, package_type: &str, summary: &str) -> String {
    let mut line = format!("{:<10} - {:.65}", package, summary);
    if package_type != "deb" && !package_type.is_empty() {
        line.push_str(&format!(" ({})", package_type));
    }
    line
}

/// Render the `.changes` document (without signature), with fields in dpkg's
/// canonical order for `CTRL_FILE_CHANGES`.
///
/// Note: the legacy `Files` field carries md5+size+section+priority+name,
/// while `Checksums-Sha1`/`Checksums-Sha256` carry the stronger hashes;
/// `Checksums-Md5` is deliberately omitted as redundant, exactly like
/// dpkg-genchanges does.
pub fn render_changes(input: &ChangesInput) -> Paragraph {
    let mut p = Paragraph::new();
    p.set("Format", "1.8");
    p.set("Date", &input.date);
    p.set("Source", &input.source);
    if !input.binaries.is_empty() {
        let joined = input.binaries.join(" ");
        p.set("Binary", &wrap_long(&joined));
    }
    if !input.built_for_profiles.is_empty() {
        p.set("Built-For-Profiles", &input.built_for_profiles.join(" "));
    }
    p.set("Architecture", &input.architecture);
    p.set("Version", &input.version);
    p.set("Distribution", &input.distribution);
    p.set("Urgency", &input.urgency);
    if let Some(maintainer) = &input.maintainer {
        p.set("Maintainer", maintainer);
    }
    if let Some(changed_by) = &input.changed_by {
        p.set("Changed-By", changed_by);
    }
    if !input.descriptions.is_empty() {
        let mut sorted = input.descriptions.clone();
        sorted.sort();
        // Leading `\n`: pre-wrapped multiline field, dpkg-style.
        p.set("Description", &format!("\n{}", sorted.join("\n")));
    }
    if let Some(closes) = &input.closes {
        p.set("Closes", closes);
    }
    p.set("Changes", &input.changes_field);

    if !input.checksums.is_empty() {
        p.set("Checksums-Sha1", &input.checksums.field_sha1());
        p.set("Checksums-Sha256", &input.checksums.field_sha256());

        // Legacy Files field: md5 size section priority filename
        let mut files = String::new();
        for (key, entry) in input.checksums.iter() {
            let (section, priority) = input
                .files_list
                .get(key)
                .map(|f| (f.section.as_str(), f.priority.as_str()))
                .unwrap_or(("-", "-"));
            files.push('\n');
            files.push_str(&entry.md5);
            files.push(' ');
            files.push_str(&entry.size.to_string());
            files.push(' ');
            files.push_str(section);
            files.push(' ');
            files.push_str(priority);
            files.push(' ');
            files.push_str(key);
        }
        p.set("Files", &files);
    }
    p
}

/// Serialize and atomically write a `.changes` file.
pub fn save_changes(path: &Path, paragraph: &Paragraph) -> Result<(), Box<dyn std::error::Error>> {
    let tmp = path.with_extension("new");
    std::fs::write(&tmp, write_paragraph(paragraph))
        .map_err(|e| format!("cannot write '{}': {}", tmp.display(), e))?;
    std::fs::rename(&tmp, path)
        .map_err(|e| format!("cannot install '{}': {}", path.display(), e).into())
}

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

    #[test]
    fn description_formatting() {
        assert_eq!(
            format_description("hello", "deb", "The classic greeting"),
            "hello      - The classic greeting"
        );
        assert_eq!(
            format_description("verylongpkgname", "udeb", "short"),
            "verylongpkgname - short (udeb)"
        );
        let long_summary = "x".repeat(100);
        assert_eq!(
            format_description("p", "deb", &long_summary).len(),
            10 + 3 + 65
        );
    }

    #[test]
    fn render_source_only_changes() {
        let dir = tempfile::tempdir().unwrap();
        let dsc_path = dir.path().join("pkg_1.0.dsc");
        std::fs::write(&dsc_path, b"content\n").unwrap();

        let mut checksums = FileChecksums::new();
        checksums.add_file(&dsc_path).unwrap();

        let mut files_list = FilesList::new();
        files_list.add(crate::debian::FilesEntry::new(
            "pkg_1.0.dsc",
            "utils",
            "optional",
        ));

        let input = ChangesInput {
            date: "Sat, 22 Aug 2026 10:00:00 +0000".to_string(),
            source: "pkg".to_string(),
            binaries: vec![],
            built_for_profiles: vec![],
            architecture: "source".to_string(),
            version: "1.0".to_string(),
            distribution: "unstable".to_string(),
            urgency: "medium".to_string(),
            maintainer: Some("A B <a@b.c>".to_string()),
            changed_by: Some("A B <a@b.c>".to_string()),
            descriptions: vec![],
            closes: None,
            changes_field: "pkg (1.0) unstable; urgency=medium\n.\n * Something.".to_string(),
            checksums,
            files_list,
        };

        let p = render_changes(&input);
        let keys: Vec<&str> = p.iter().map(|(k, _)| k).collect();
        assert_eq!(
            keys,
            vec![
                "Format",
                "Date",
                "Source",
                "Architecture",
                "Version",
                "Distribution",
                "Urgency",
                "Maintainer",
                "Changed-By",
                "Changes",
                "Checksums-Sha1",
                "Checksums-Sha256",
                "Files"
            ]
        );
        // No Binary / Description / Checksums-Md5 for source-only uploads.
        assert!(p.get("Binary").is_none());
        assert!(p.get("Description").is_none());
        assert!(p.get("Checksums-Md5").is_none());

        let files_value = p.get("Files").unwrap();
        assert_eq!(
            files_value,
            "\n<md5> 8 utils optional pkg_1.0.dsc"
                .replace("<md5>", files_value.split_whitespace().next().unwrap_or(""))
        );
    }
}