llmx/codex-rs/core/src/config.rs

use dirs::home_dir;
use serde::Deserialize;

/// Embedded fallback instructions that mirror the TypeScript CLI’s default system prompt. These
/// are compiled into the binary so a clean install behaves correctly even if the user has not
/// created `~/.codex/instructions.md`.
const EMBEDDED_INSTRUCTIONS: &str = include_str!("../prompt.md");

#[derive(Default, Deserialize, Debug, Clone)]
pub struct Config {
    pub model: Option<String>,
    pub instructions: Option<String>,
}

impl Config {
    /// Load ~/.codex/config.toml and ~/.codex/instructions.md (if present).
    /// Returns `None` if neither file exists.
    pub fn load() -> Option<Self> {
        let mut cfg: Config = Self::load_from_toml().unwrap_or_default();

        // Highest precedence → user‑provided ~/.codex/instructions.md (if present)
        // Fallback           → embedded default instructions baked into the binary

        cfg.instructions =
            Self::load_instructions().or_else(|| Some(EMBEDDED_INSTRUCTIONS.to_string()));

        Some(cfg)
    }

    fn load_from_toml() -> Option<Self> {
        let mut p = home_dir()?;
        p.push(".codex/config.toml");
        let contents = std::fs::read_to_string(&p).ok()?;
        toml::from_str(&contents).ok()
    }

    fn load_instructions() -> Option<String> {
        let mut p = home_dir()?;
        p.push(".codex/instructions.md");
        std::fs::read_to_string(&p).ok()
    }
}