use std::env;
use std::path::PathBuf;

#[derive(Debug, Clone)]
pub struct Config {
    pub api_key: String,
    pub base_url: String,
    pub model: String,
}

/// Copy GROKBOY_* process env into LAZYBOY_* when the new name is unset.
pub fn alias_legacy_env() {
    let inherited: Vec<(String, String)> = env::vars()
        .filter_map(|(key, value)| {
            key.strip_prefix("GROKBOY_")
                .map(|rest| (format!("LAZYBOY_{rest}"), value))
        })
        .collect();
    for (key, value) in inherited {
        if env::var_os(&key).is_none() {
            unsafe { env::set_var(key, value) };
        }
    }
}

/// ~/.lazyboy, or ~/.grokboy if that already has data and the new dir does not.
pub fn home_config_dir() -> Option<PathBuf> {
    let home = home_dir()?;
    let neu = home.join(".lazyboy");
    let old = home.join(".grokboy");
    if neu.exists() || !old.exists() {
        Some(neu)
    } else {
        Some(old)
    }
}

/// Load `.env` files and map legacy GROKBOY_* names to LAZYBOY_*.
pub fn bootstrap_env() {
    load_dotenv_files();
    alias_legacy_env();
}

impl Config {
    /// Resolve from environment, then dotenv files, then a logged-in Grok CLI session.
    pub fn from_env() -> Result<Self, String> {
        bootstrap_env();
        let api_key = env::var("LAZYBOY_API_KEY")
            .or_else(|_| env::var("XAI_API_KEY"))
            .or_else(|_| env::var("OPENAI_API_KEY"))
            .ok()
            .map(|s| s.trim().to_string())
            .filter(|s| !s.is_empty())
            .or_else(grok_cli_auth_key)
            .ok_or_else(|| {
                "沒有 API key。設 LAZYBOY_API_KEY（或 XAI_API_KEY），或先用 Grok CLI 登入（~/.grok/auth.json）。"
                    .to_string()
            })?;
        let base_url = env::var("LAZYBOY_BASE_URL")
            .or_else(|_| env::var("OPENAI_BASE_URL"))
            .unwrap_or_else(|_| "https://api.x.ai/v1".into());
        let model = env::var("LAZYBOY_MODEL").unwrap_or_else(|_| "grok-4.6".into());
        Ok(Self {
            api_key,
            base_url: base_url.trim_end_matches('/').to_string(),
            model,
        })
    }
}

fn home_dir() -> Option<PathBuf> {
    env::var_os("HOME")
        .or_else(|| env::var_os("USERPROFILE"))
        .map(PathBuf::from)
}

fn load_dotenv_files() {
    let mut paths = Vec::new();
    if let Ok(cwd) = env::current_dir() {
        paths.push(cwd.join(".env"));
    }
    if let Some(home) = home_dir() {
        paths.push(home.join(".lazyboy").join(".env"));
        paths.push(home.join(".lazyboy").join("env"));
        paths.push(home.join(".grokboy").join(".env"));
        paths.push(home.join(".grokboy").join("env"));
    }
    for path in paths {
        let Ok(text) = std::fs::read_to_string(&path) else {
            continue;
        };
        for line in text.lines() {
            let line = line.trim();
            if line.is_empty() || line.starts_with('#') {
                continue;
            }
            let Some((key, value)) = line.split_once('=') else {
                continue;
            };
            let key = key.trim();
            let canonical = if let Some(rest) = key.strip_prefix("GROKBOY_") {
                format!("LAZYBOY_{rest}")
            } else {
                key.to_string()
            };
            if !canonical.starts_with("LAZYBOY_")
                && !matches!(
                    canonical.as_str(),
                    "XAI_API_KEY" | "OPENAI_API_KEY" | "OPENAI_BASE_URL"
                )
            {
                continue;
            }
            if env::var_os(&canonical).is_some() {
                continue;
            }
            let value = value
                .trim()
                .trim_matches('"')
                .trim_matches('\'')
                .to_string();
            if !value.is_empty() {
                // dotenv only fills keys that are not already in the process environment.
                unsafe { env::set_var(canonical, value) };
            }
        }
    }
}

fn grok_cli_auth_key() -> Option<String> {
    let path = home_dir()?.join(".grok").join("auth.json");
    let raw = std::fs::read_to_string(path).ok()?;
    let value: serde_json::Value = serde_json::from_str(&raw).ok()?;
    grok_cli_key_from_value(&value)
}

pub(crate) fn grok_cli_key_from_value(value: &serde_json::Value) -> Option<String> {
    let obj = value.as_object()?;
    let mut newest: Option<(String, String)> = None;
    for (_id, entry) in obj {
        let Some(key) = entry
            .get("key")
            .and_then(|v| v.as_str())
            .map(str::trim)
            .filter(|s| !s.is_empty())
        else {
            continue;
        };
        let created = entry
            .get("create_time")
            .and_then(|v| v.as_str())
            .unwrap_or("")
            .to_string();
        if newest
            .as_ref()
            .is_none_or(|(prev, _)| created.as_str() >= prev.as_str())
        {
            newest = Some((created, key.to_string()));
        }
    }
    newest.map(|(_, key)| key)
}

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

    #[test]
    fn default_model_is_grok_4_6() {
        let cfg = Config {
            api_key: "x".into(),
            base_url: "https://api.x.ai/v1".into(),
            model: "grok-4.6".into(),
        };
        assert_eq!(cfg.model, "grok-4.6");
    }

    #[test]
    fn rejects_missing_key() {
        let _ = Config {
            api_key: "x".into(),
            base_url: "https://api.x.ai/v1".into(),
            model: "grok-4.6".into(),
        };
    }

    #[test]
    fn grok_cli_auth_json_yields_key() {
        let value = serde_json::json!({
            "https://auth.x.ai::older": {
                "key": "old-token",
                "create_time": "2026-01-01T00:00:00.000000Z"
            },
            "https://auth.x.ai::newer": {
                "key": "new-token",
                "create_time": "2026-09-01T00:00:00.000000Z"
            }
        });
        assert_eq!(grok_cli_key_from_value(&value).as_deref(), Some("new-token"));
    }
}