use std::path::Path;

/// cwd, platform, date, best-effort git status. Kept as its own block (not merged into the
/// agent prompt) because Anthropic cache breakpoints need the system prompt structured as
/// separate blocks (see `LlmRequest.system: Vec<String>`).
pub fn env_header(cwd: &Path) -> String {
    let git_status = std::process::Command::new("git")
        .arg("status")
        .arg("--short")
        .current_dir(cwd)
        .output()
        .ok()
        .filter(|o| o.status.success())
        .map(|o| String::from_utf8_lossy(&o.stdout).trim().to_string())
        .filter(|s| !s.is_empty());

    let mut header = format!(
        "Working directory: {}\nPlatform: {}\n",
        cwd.display(),
        std::env::consts::OS
    );
    if let Some(status) = git_status {
        header.push_str(&format!("Git status:\n{status}\n"));
    }
    header
}

/// Ordered system prompt blocks: environment header, agent prompt, then project
/// instructions (e.g. AGENTS.md contents). Order matches `02-engine.md`.
pub fn assemble(env_header: String, agent_prompt: &str, instructions: &[String]) -> Vec<String> {
    let mut blocks = vec![env_header, agent_prompt.to_string()];
    blocks.extend(instructions.iter().cloned());
    blocks
}

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

    #[test]
    fn env_header_includes_cwd_and_platform() {
        let header = env_header(Path::new("."));
        assert!(header.contains("Working directory:"));
        assert!(header.contains(std::env::consts::OS));
    }

    #[test]
    fn assemble_orders_env_agent_then_instructions() {
        let blocks = assemble(
            "ENV".to_string(),
            "AGENT",
            &["AGENTS.md contents".to_string()],
        );
        assert_eq!(blocks, vec!["ENV", "AGENT", "AGENTS.md contents"]);
    }
}