//! 配置加载。
//! Configuration loading.
//!
//! 读取 `~/.focus/config.json`（可通过 `FOCUS_CONFIG_DIR` 覆盖）。该文件列出
//! provider 与一个默认值；API-key 的值可以是 `$VAR`/`${VAR}` 模板，在加载时
//! 解析（见 [`focus_providers::resolve_config_value`]）。
//! Reads `~/.focus/config.json` (overridable via `FOCUS_CONFIG_DIR`). The file
//! lists providers and a default; API-key values may be `$VAR`/`${VAR}`
//! templates resolved at load time (see [`focus_providers::resolve_config_value`]).
//!
//! 示例配置：
//! Example config:
//! ```json
//! {
//!   "default": "zai-coding-cn",
//!   "providers": {
//!     "zai-coding-cn": {
//!       "kind": "zai",
//!       "region": "cn",
//!       "model": "glm-5.2",
//!       "path": "/api/coding/paas/v4/chat/completions",
//!       "apiKey": "$ZAI_API_KEY"
//!     }
//!   }
//! }
//! ```
//!
//! `path` 字段用于选择接入档位：对 `xxxxxxxx.yyyyyyyy` 格式的 key 使用 GLM
//! Coding Plan（`/api/coding/paas/v4/chat/completions`），对按量付费 key 使用
//! 标准 PaaS（`/api/paas/v4/chat/completions`）。省略时使用 provider 的默认路径。
//! The `path` field selects the access tier: the GLM Coding Plan
//! (`/api/coding/paas/v4/chat/completions`) for `xxxxxxxx.yyyyyyyy` keys, or
//! the standard PaaS (`/api/paas/v4/chat/completions`) for pay-as-you-go keys.
//! When omitted, the provider's default path is used.

use focus_json::{parse, JsonValue};
use std::path::{Path, PathBuf};

/// 加载配置时出现的错误。
/// Errors while loading config.
#[derive(Debug)]
pub enum ConfigError {
    /// I/O 错误（例如读取文件失败）。
    /// An I/O error (e.g. failed to read the file).
    Io(String),
    /// JSON 解析错误。
    /// A JSON parse error.
    Parse(String),
    /// 缺少必需字段。
    /// A required field is missing.
    Missing(String),
}

impl std::fmt::Display for ConfigError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            ConfigError::Io(m) => write!(f, "config io error: {}", m),
            ConfigError::Parse(m) => write!(f, "config parse error: {}", m),
            ConfigError::Missing(m) => write!(f, "config missing: {}", m),
        }
    }
}

impl std::error::Error for ConfigError {}

/// 已解析的 provider 条目。
/// A resolved provider entry.
#[derive(Debug, Clone)]
pub struct ProviderEntry {
    /// provider 种类（如 `zai`、`openai`、`anthropic`）。
    /// Provider kind (e.g. `zai`, `openai`, `anthropic`).
    pub kind: String,
    /// 国内为 `"cn"`，国际为 `"intl"`（仅 zai 适用）。
    /// `"cn"` for domestic, `"intl"` for international (zai only).
    pub region: String,
    /// 默认模型 id。
    /// The default model id.
    pub model: String,
    /// 已解析的 API key（加载时由 `$VAR`/`${VAR}` 模板展开而来）。
    /// Resolved API key (expanded from `$VAR`/`${VAR}` templates at load time).
    pub api_key: String,
    /// 可选的自定义 base host（覆盖区域默认值）。
    /// Optional custom base host (overrides the region default).
    pub base_url: Option<String>,
    /// 可选的 chat-completions 路径覆盖（例如为 `xxxxxxxx.yyyyyyyy` 格式的 key
    /// 指定 GLM Coding Plan 路径 `/api/coding/paas/v4/chat/completions`）。
    /// 未设置时使用 provider 的默认路径。
    /// Optional chat-completions path override (e.g. the GLM Coding Plan path
    /// `/api/coding/paas/v4/chat/completions` for `xxxxxxxx.yyyyyyyy` keys).
    /// When unset, the provider's default path is used.
    pub path: Option<String>,
}

/// 已加载的配置。
/// The loaded configuration.
#[derive(Debug, Clone)]
pub struct Config {
    /// 默认 provider 名称。
    /// The default provider name.
    pub default: String,
    /// 全部 provider 条目（名称, 条目）的有序列表。
    /// All provider entries as an ordered list of (name, entry).
    pub providers: Vec<(String, ProviderEntry)>,
}

impl Config {
    /// 一个没有任何 provider 的空配置。当配置文件尚不存在时作为回退，
    /// 这样 CLI 可以打印引导信息而不是崩溃。
    /// An empty config with no providers. Used as a fallback when the config
    /// file does not exist yet, so the CLI can print guidance instead of
    /// crashing.
    pub fn empty() -> Self {
        Self {
            default: String::new(),
            providers: Vec::new(),
        }
    }

    /// 未配置任何 provider 时为真。
    /// True if no providers are configured.
    pub fn is_empty(&self) -> bool {
        self.providers.is_empty()
    }

    /// 返回默认 provider 条目；若默认值未设置或未知则返回 None。
    /// Get the default provider entry, or None if the default is unset/unknown.
    #[cfg(test)]
    pub fn default_provider(&self) -> Option<(&str, &ProviderEntry)> {
        self.providers
            .iter()
            .find(|(name, _)| name == &self.default)
            .map(|(n, e)| (n.as_str(), e))
    }

    /// 按名称获取 provider 条目。
    /// Get a named provider entry.
    pub fn provider(&self, name: &str) -> Option<&ProviderEntry> {
        self.providers
            .iter()
            .find(|(n, _)| n == name)
            .map(|(_, e)| e)
    }
}

/// 解析配置目录：`$FOCUS_CONFIG_DIR` 或 `~/.focus`。
/// Resolve the config directory: `$FOCUS_CONFIG_DIR` or `~/.focus`.
pub fn config_dir() -> Result<PathBuf, ConfigError> {
    if let Ok(dir) = std::env::var("FOCUS_CONFIG_DIR") {
        return Ok(PathBuf::from(dir));
    }
    let home = std::env::var("HOME").map_err(|_| ConfigError::Io("HOME is not set".into()))?;
    Ok(PathBuf::from(home).join(".focus"))
}

/// 从默认路径（`~/.focus/config.json`）加载配置。
/// Load config from the default path (`~/.focus/config.json`).
///
/// 若文件不存在，则返回内置默认 provider（这样 CLI 开箱即用：
/// `focus login zai` + `focus "你好"`）。文件存在但不可读、格式错误或缺少
/// 必需字段时仍视为错误。
/// If the file does not exist, returns the built-in default providers (so the
/// CLI works out of the box: `focus login zai` + `focus "你好"`). A file that
/// exists but is unreadable, malformed, or missing required fields is still an
/// error.
pub fn load() -> Result<Config, ConfigError> {
    let path = config_dir()?.join("config.json");
    if !path.exists() {
        return Ok(builtin_defaults());
    }
    load_from(&path)
}

/// 当 `config.json` 不存在时使用的内置默认 provider。它们让 focus 对主要目标
/// （Z.ai / 智谱 GLM Coding Plan）及其它受支持厂商开箱即用。API key 通过
/// `focus login` 或 `--api-key` 单独提供。
/// The built-in default providers used when no `config.json` exists. These make
/// focus work out of the box for the primary target (Z.ai / 智谱 GLM Coding
/// Plan) plus the other supported vendors. API keys are supplied separately via
/// `focus login` or `--api-key`.
///
/// 默认的 `zai-coding-cn` 指向 **GLM Coding Plan** 档位，该档位的 key
/// （`xxxxxxxx.yyyyyyyy` 格式）必须使用 `/api/coding/paas/v4/chat/completions`——
/// 标准 `/api/paas/v4/...` 路径会对这类 key 返回 `429 余额不足`。
/// The default `zai-coding-cn` targets the **GLM Coding Plan** tier, whose keys
/// (`xxxxxxxx.yyyyyyyy` format) must use `/api/coding/paas/v4/chat/completions`
/// — the standard `/api/paas/v4/...` path reports `429 余额不足` for them.
pub fn builtin_defaults() -> Config {
    let mk = |kind: &str, region: &str, model: &str, base_url: Option<&str>, path: Option<&str>| {
        ProviderEntry {
            kind: kind.to_string(),
            region: region.to_string(),
            model: model.to_string(),
            api_key: String::new(),
            base_url: base_url.map(String::from),
            path: path.map(String::from),
        }
    };
    Config {
        default: "zai-coding-cn".to_string(),
        providers: vec![
            (
                "zai-coding-cn".to_string(),
                mk(
                    "zai",
                    "cn",
                    "glm-5.2",
                    None,
                    Some(focus_providers::ZAI_CODING_PATH),
                ),
            ),
            (
                "zai-coding-intl".to_string(),
                mk(
                    "zai",
                    "intl",
                    "glm-5.2",
                    None,
                    Some(focus_providers::ZAI_CODING_PATH),
                ),
            ),
            // 标准按量付费 PaaS 档位（与 coding plan 区分开）。
            // Standard pay-as-you-go PaaS tier (separate from the coding plan).
            ("zai-cn".to_string(), mk("zai", "cn", "glm-5.2", None, None)),
            (
                "zai-intl".to_string(),
                mk("zai", "intl", "glm-5.2", None, None),
            ),
            (
                "anthropic".to_string(),
                mk("anthropic", "", "claude-sonnet-4-5", None, None),
            ),
            ("openai".to_string(), mk("openai", "", "gpt-4o", None, None)),
        ],
    }
}

/// 从显式路径加载配置。便于测试。
/// Load config from an explicit path. Useful for tests.
pub fn load_from(path: &Path) -> Result<Config, ConfigError> {
    // 配置文件缺失不是错误——返回空配置，让调用者决定如何引导用户。
    // A missing config file is not an error — return an empty config so the
    // caller can decide how to guide the user.
    if !path.exists() {
        return Ok(Config::empty());
    }
    let text = std::fs::read_to_string(path)
        .map_err(|e| ConfigError::Io(format!("read {}: {}", path.display(), e)))?;
    let value = parse(&text).map_err(|e| ConfigError::Parse(e.to_string()))?;
    parse_config(&value)
}

/// 将解析后的 JSON 值转换为 [`Config`]。
/// Convert a parsed JSON value into a [`Config`].
fn parse_config(value: &JsonValue) -> Result<Config, ConfigError> {
    let default = value
        .get_str("default")
        .ok_or_else(|| ConfigError::Missing("missing 'default' provider name".into()))?
        .to_string();
    let providers_obj = value
        .get("providers")
        .ok_or_else(|| ConfigError::Missing("missing 'providers' object".into()))?;
    let entries = match providers_obj {
        JsonValue::Obj(e) => e,
        _ => return Err(ConfigError::Parse("'providers' must be an object".into())),
    };
    let mut providers = Vec::new();
    for (name, entry) in entries {
        let kind = entry
            .get_str("kind")
            .ok_or_else(|| ConfigError::Missing(format!("provider '{}' missing 'kind'", name)))?
            .to_string();
        let region = entry.get_str("region").unwrap_or("cn").to_string();
        let model = entry
            .get_str("model")
            .ok_or_else(|| ConfigError::Missing(format!("provider '{}' missing 'model'", name)))?
            .to_string();
        // apiKey 在 config.json 中是可选的——key 通常通过 `focus login`（auth.json）
        // 或 --api-key 提供。若缺失则默认为空，后续解析会失败并给出友好提示。
        // apiKey is optional in config.json — the key is usually supplied via
        // `focus login` (auth.json) or --api-key. If absent, it defaults to
        // empty and resolution fails later with a helpful message.
        let raw_key = entry.get_str("apiKey").unwrap_or("");
        let api_key = if raw_key.is_empty() {
            String::new()
        } else {
            focus_providers::resolve_config_value(raw_key).map_err(ConfigError::Io)?
        };
        let base_url = entry.get_str("baseUrl").map(String::from);
        let path = entry.get_str("path").map(String::from);
        providers.push((
            name.clone(),
            ProviderEntry {
                kind,
                region,
                model,
                api_key,
                base_url,
                path,
            },
        ));
    }
    Ok(Config { default, providers })
}

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

    #[test]
    fn parses_minimal_config() {
        let text = r#"{
            "default": "zai-coding-cn",
            "providers": {
                "zai-coding-cn": {
                    "kind": "zai",
                    "region": "cn",
                    "model": "glm-5.2",
                    "apiKey": "literal-key"
                }
            }
        }"#;
        let v = parse(text).unwrap();
        let cfg = parse_config(&v).unwrap();
        assert_eq!(cfg.default, "zai-coding-cn");
        let (_, entry) = cfg.default_provider().unwrap();
        assert_eq!(entry.kind, "zai");
        assert_eq!(entry.region, "cn");
        assert_eq!(entry.model, "glm-5.2");
        assert_eq!(entry.api_key, "literal-key");
    }

    #[test]
    fn resolves_env_var_key() {
        env::set_var("FOCUS_CFG_TEST_KEY", "env-secret");
        let text = r#"{
            "default": "zai",
            "providers": {
                "zai": { "kind": "zai", "model": "m", "apiKey": "$FOCUS_CFG_TEST_KEY" }
            }
        }"#;
        let v = parse(text).unwrap();
        let cfg = parse_config(&v).unwrap();
        assert_eq!(cfg.provider("zai").unwrap().api_key, "env-secret");
    }

    #[test]
    fn provider_without_apikey_is_accepted() {
        // apiKey 是可选的——key 通过 `focus login` 或 --api-key 提供。
        // apiKey is optional — the key is supplied via `focus login` or --api-key.
        let text = r#"{
            "default": "zai-coding-cn",
            "providers": {
                "zai-coding-cn": { "kind": "zai", "region": "cn", "model": "glm-5.2" }
            }
        }"#;
        let v = parse(text).unwrap();
        let cfg = parse_config(&v).unwrap();
        let entry = cfg.provider("zai-coding-cn").unwrap();
        assert_eq!(entry.model, "glm-5.2");
        assert_eq!(entry.api_key, "");
    }

    #[test]
    fn rejects_missing_default() {
        let v = parse(r#"{"providers":{}}"#).unwrap();
        assert!(parse_config(&v).is_err());
    }

    #[test]
    fn rejects_unknown_default() {
        let text = r#"{
            "default": "nope",
            "providers": {
                "zai": { "kind": "zai", "model": "m", "apiKey": "k" }
            }
        }"#;
        let v = parse(text).unwrap();
        let cfg = parse_config(&v).unwrap();
        assert!(cfg.default_provider().is_none());
    }

    #[test]
    fn missing_file_returns_empty_config() {
        // 不存在的路径不是错误——返回空配置，以便 CLI 打印安装引导而不是崩溃。
        // A nonexistent path is NOT an error — returns an empty config so the
        // CLI can print setup guidance instead of crashing.
        let path = Path::new("/nonexistent/focus/config-test-does-not-exist.json");
        assert!(!path.exists());
        let cfg = load_from(path).expect("missing file should not error");
        assert!(cfg.is_empty());
        assert_eq!(cfg.default, "");
    }

    #[test]
    fn malformed_file_is_an_error() {
        // 文件存在但 JSON 无效才是真正的错误。
        // A file that exists but has invalid JSON is a real error.
        let dir = std::env::temp_dir();
        let path = dir.join("focus-malformed-test.json");
        std::fs::write(&path, "{ this is not valid json").unwrap();
        let result = load_from(&path);
        assert!(result.is_err());
        let _ = std::fs::remove_file(&path);
    }
}