//! Versions of main. Each landing adds one; each version names the one
//! before it, so main is a hash chain.

use serde::{Deserialize, Serialize};

use crate::Id;
use crate::id::sha256;

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct Version {
    pub n: u64,
    pub tree: Id,
    /// The previous version's ID (None for version 1).
    pub prev: Option<Id>,
    /// The change that landed (empty for imported history).
    pub change: String,
    /// "Name <email>", the person (or agent acting for one) who wrote it.
    pub author: String,
    /// Seconds since the epoch.
    pub time: i64,
    pub title: String,
    #[serde(default)]
    pub body: String,
    /// The git commit this version is in the project's git view, once known.
    #[serde(default)]
    pub git: Option<String>,
}

impl Version {
    /// The version's ID: a hash of everything but its git mapping, which is
    /// filled in later.
    pub fn id(&self, project: &str) -> Id {
        let text = format!(
            "vcs version\nproject {project}\nn {}\ntree {}\nprev {}\nchange {}\nauthor {}\ntime {}\n\n{}\n\n{}",
            self.n,
            self.tree,
            self.prev.map(|p| p.hex()).unwrap_or_else(|| "-".into()),
            self.change,
            self.author,
            self.time,
            self.title,
            self.body
        );
        sha256(&[text.as_bytes()])
    }

    /// The description as one text: title, a blank line, then the body.
    pub fn message(&self) -> String {
        if self.body.is_empty() { self.title.clone() } else { format!("{}\n\n{}", self.title, self.body) }
    }
}

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

    #[test]
    fn ids_chain() {
        let v1 = Version { n: 1, tree: Id::ZERO, prev: None, change: "bcdf".into(), author: "a <a@x>".into(), time: 1, title: "t".into(), body: String::new(), git: None };
        let v2 = Version { n: 2, prev: Some(v1.id("p")), ..v1.clone() };
        assert_ne!(v1.id("p"), v2.id("p"));
        let mut mapped = v1.clone();
        mapped.git = Some("abc".into());
        assert_eq!(mapped.id("p"), v1.id("p"));
    }
}