//! Managed gitconfig and hook shims, written into the data dir at boot.

use std::fs::{self, File};
use std::io::Write;
use std::os::unix::fs::PermissionsExt;
use std::path::Path;

use crate::error::{Error, Result};

/// Quotes a value for a git config file. Control characters are rejected.
fn quote_config_value(v: &str) -> Result<String> {
    if v.chars().any(char::is_control) {
        return Err(Error::InvalidInput(format!(
            "config value contains control characters: {v:?}"
        )));
    }
    Ok(format!(
        "\"{}\"",
        v.replace('\\', "\\\\").replace('"', "\\\"")
    ))
}

/// Writes `name` in `dir` atomically: temp file, fsync, rename, then fsync the directory.
fn write_atomic(dir: &Path, name: &str, contents: &[u8], mode: u32) -> Result<()> {
    let tmp = dir.join(format!(".{name}.tmp"));
    {
        let mut f = fs::OpenOptions::new()
            .write(true)
            .create(true)
            .truncate(true)
            .open(&tmp)?;
        f.write_all(contents)?;
        f.set_permissions(fs::Permissions::from_mode(mode))?;
        f.sync_all()?;
    }
    fs::rename(&tmp, dir.join(name))?;
    File::open(dir)?.sync_all()?;
    Ok(())
}

/// Writes `data_dir/gitconfig`: core.hooksPath, fsck, fsync, uploadpack and receive settings.
pub fn write_managed_gitconfig(data_dir: &Path) -> Result<()> {
    if !data_dir.is_absolute() {
        return Err(Error::InvalidInput(format!(
            "data dir must be absolute: {}",
            data_dir.display()
        )));
    }
    let hooks = data_dir.join("hooks");
    let hooks = hooks
        .to_str()
        .ok_or_else(|| Error::InvalidInput("data dir is not valid UTF-8".into()))?;
    let hooks = quote_config_value(hooks)?;

    // `committed` hardens loose objects and packs; `reference` hardens ref updates.
    let body = format!(
        "[core]\n\
         \thooksPath = {hooks}\n\
         \tfsync = committed,reference\n\
         \tfsyncMethod = fsync\n\
         \tcommitGraph = true\n\
         [receive]\n\
         \tfsckObjects = true\n\
         \tadvertisePushOptions = true\n\
         \tdenyNonFastForwards = false\n\
         [transfer]\n\
         \tfsckObjects = true\n\
         \thideRefs = refs/forge-internal/\n\
         [fetch]\n\
         \tfsckObjects = true\n\
         \twriteCommitGraph = true\n\
         [uploadpack]\n\
         \tallowFilter = true\n\
         \tallowRefInWant = true\n\
         \thideRefs = refs/forge-internal/\n\
         [protocol \"file\"]\n\
         \tallow = never\n\
         [protocol \"ext\"]\n\
         \tallow = never\n"
    );
    fs::create_dir_all(data_dir)?;
    write_atomic(data_dir, "gitconfig", body.as_bytes(), 0o644)
}

/// Writes `data_dir/hooks/{pre-receive,post-receive}` as `exec <forge_bin> hook <name>`, mode 0755.
/// `forge_bin` must be absolute and contain no quotes or control characters.
pub fn write_hook_shims(data_dir: &Path, forge_bin: &Path) -> Result<()> {
    let bin = forge_bin
        .to_str()
        .ok_or_else(|| Error::InvalidInput("forge binary path is not valid UTF-8".into()))?;
    if !forge_bin.is_absolute() {
        return Err(Error::InvalidInput(format!(
            "forge binary path must be absolute: {bin}"
        )));
    }
    if bin.chars().any(|c| c == '\'' || c.is_control()) {
        return Err(Error::InvalidInput(format!(
            "forge binary path contains a quote or control character: {bin:?}"
        )));
    }
    let hooks = data_dir.join("hooks");
    fs::create_dir_all(&hooks)?;
    for name in ["pre-receive", "post-receive"] {
        let body = format!("#!/bin/sh\nexec '{bin}' hook {name}\n");
        write_atomic(&hooks, name, body.as_bytes(), 0o755)?;
    }
    Ok(())
}

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

    #[test]
    fn managed_gitconfig_enables_commit_graph() {
        let tmp = tempfile::tempdir().expect("tempdir");
        write_managed_gitconfig(tmp.path()).expect("write gitconfig");
        let body = fs::read_to_string(tmp.path().join("gitconfig")).expect("read gitconfig");
        assert!(body.contains("\tcommitGraph = true\n"));
        assert!(body.contains("\twriteCommitGraph = true\n"));
        assert!(
            !body.contains("gc.auto"),
            "gc.auto must stay at its default"
        );
    }
}