//! Configuration (hub spec §17.1): `hub.toml` in the data directory, every
//! key overridable by `OXYHUB_<SECTION>_<KEY>`.

use serde::Deserialize;
use std::net::SocketAddr;
use std::path::{Path, PathBuf};

#[derive(Clone, Debug, Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct Config {
    /// Set from the command line, never from the file.
    #[serde(skip)]
    pub data: PathBuf,
    pub site: Site,
    pub server: Server,
    pub tls: Tls,
    pub auth: Auth,
    pub limits: Limits,
    pub retention: Retention,
}

#[derive(Clone, Debug, Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct Site {
    pub name: String,
    pub description: String,
}

#[derive(Clone, Debug, Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct Server {
    /// Plain HTTP; empty disables it.
    pub bind: String,
    /// HTTPS; empty disables it. Needs `tls`.
    pub tls_bind: String,
    /// What links and clone URLs start with.
    pub base_url: String,
    /// Trust `X-Forwarded-*` from a terminating proxy.
    pub behind_proxy: bool,
}

#[derive(Clone, Debug, Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct Tls {
    /// Generate a certificate at `init` (developer edition).
    pub self_signed: bool,
    /// PEM files; relative paths are under the data directory.
    pub cert: String,
    pub key: String,
}

#[derive(Clone, Debug, Default, Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct Auth {
    /// Bearer tokens allowed to push until accounts exist (hub 0.2). Empty
    /// means every push is accepted, as `oxy serve` does.
    pub push_tokens: Vec<String>,
}

#[derive(Clone, Debug, Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct Limits {
    /// Largest file rendered in the browser, e.g. `2MiB`.
    pub render_limit: ByteSize,
    pub asset_limit: ByteSize,
    pub push_body_limit: ByteSize,
}

#[derive(Clone, Debug, Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct Retention {
    pub trash_days: u32,
    pub webhook_log_days: u32,
}

/// A byte count written as `512`, `2MiB`, `4GiB`, `100kB`.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct ByteSize(pub u64);

impl ByteSize {
    pub fn parse(s: &str) -> Option<ByteSize> {
        let s = s.trim();
        let digits: String = s.chars().take_while(|c| c.is_ascii_digit()).collect();
        let unit = s[digits.len()..].trim();
        let n: u64 = digits.parse().ok()?;
        let mult = match unit {
            "" | "B" => 1,
            "k" | "kB" | "KB" => 1000,
            "KiB" | "K" => 1 << 10,
            "M" | "MB" => 1_000_000,
            "MiB" => 1 << 20,
            "G" | "GB" => 1_000_000_000,
            "GiB" => 1 << 30,
            _ => return None,
        };
        Some(ByteSize(n.checked_mul(mult)?))
    }
}

impl<'de> Deserialize<'de> for ByteSize {
    fn deserialize<D: serde::Deserializer<'de>>(d: D) -> Result<ByteSize, D::Error> {
        #[derive(Deserialize)]
        #[serde(untagged)]
        enum Raw {
            Number(u64),
            Text(String),
        }
        match Raw::deserialize(d)? {
            Raw::Number(n) => Ok(ByteSize(n)),
            Raw::Text(t) => ByteSize::parse(&t).ok_or_else(|| serde::de::Error::custom(format!("not a byte size: {t:?}"))),
        }
    }
}

impl Default for Site {
    fn default() -> Self {
        Site { name: "Oxygenhub".into(), description: "Repositories, proposals and issues for Oxygen".into() }
    }
}

impl Default for Server {
    fn default() -> Self {
        Server { bind: "127.0.0.1:7300".into(), tls_bind: String::new(), base_url: "http://127.0.0.1:7300".into(), behind_proxy: false }
    }
}

impl Default for Tls {
    fn default() -> Self {
        Tls { self_signed: false, cert: "keys/tls.crt".into(), key: "keys/tls.key".into() }
    }
}

impl Default for Limits {
    fn default() -> Self {
        Limits { render_limit: ByteSize(2 << 20), asset_limit: ByteSize(512 << 20), push_body_limit: ByteSize(4 << 30) }
    }
}

impl Default for Retention {
    fn default() -> Self {
        Retention { trash_days: 30, webhook_log_days: 30 }
    }
}

impl Default for Config {
    fn default() -> Self {
        Config {
            data: PathBuf::from("data"),
            site: Site::default(),
            server: Server::default(),
            tls: Tls::default(),
            auth: Auth::default(),
            limits: Limits::default(),
            retention: Retention::default(),
        }
    }
}

impl Config {
    /// Read `<data>/hub.toml` if present, then apply environment overrides.
    pub fn load(data: &Path) -> anyhow::Result<Config> {
        let path = data.join("hub.toml");
        let mut cfg = match std::fs::read_to_string(&path) {
            Ok(text) => Config::parse(&text)?,
            Err(e) if e.kind() == std::io::ErrorKind::NotFound => Config::default(),
            Err(e) => return Err(anyhow::anyhow!("reading {}: {e}", path.display())),
        };
        cfg.data = data.to_path_buf();
        cfg.apply_env(|k| std::env::var(k).ok());
        Ok(cfg)
    }

    pub fn parse(text: &str) -> anyhow::Result<Config> {
        Ok(toml::from_str(text)?)
    }

    /// `OXYHUB_SERVER_BIND`, `OXYHUB_SITE_NAME`, … override the file.
    pub fn apply_env(&mut self, get: impl Fn(&str) -> Option<String>) {
        if let Some(v) = get("OXYHUB_SITE_NAME") {
            self.site.name = v;
        }
        if let Some(v) = get("OXYHUB_SITE_DESCRIPTION") {
            self.site.description = v;
        }
        if let Some(v) = get("OXYHUB_SERVER_BIND") {
            self.server.bind = v;
        }
        if let Some(v) = get("OXYHUB_SERVER_TLS_BIND") {
            self.server.tls_bind = v;
        }
        if let Some(v) = get("OXYHUB_SERVER_BASE_URL") {
            self.server.base_url = v;
        }
        if let Some(v) = get("OXYHUB_SERVER_BEHIND_PROXY") {
            self.server.behind_proxy = matches!(v.as_str(), "1" | "true" | "yes");
        }
        if let Some(v) = get("OXYHUB_TLS_SELF_SIGNED") {
            self.tls.self_signed = matches!(v.as_str(), "1" | "true" | "yes");
        }
        if let Some(v) = get("OXYHUB_AUTH_PUSH_TOKENS") {
            self.auth.push_tokens = v.split(',').map(str::trim).filter(|s| !s.is_empty()).map(String::from).collect();
        }
        if let Some(v) = get("OXYHUB_LIMITS_RENDER_LIMIT").and_then(|v| ByteSize::parse(&v)) {
            self.limits.render_limit = v;
        }
    }

    pub fn bind_addr(&self) -> anyhow::Result<Option<SocketAddr>> {
        parse_addr(&self.server.bind)
    }

    pub fn tls_bind_addr(&self) -> anyhow::Result<Option<SocketAddr>> {
        parse_addr(&self.server.tls_bind)
    }

    pub fn tls_cert(&self) -> PathBuf {
        self.data.join(&self.tls.cert)
    }

    pub fn tls_key(&self) -> PathBuf {
        self.data.join(&self.tls.key)
    }

    pub fn repos_dir(&self) -> PathBuf {
        self.data.join("repos")
    }

    pub fn keys_dir(&self) -> PathBuf {
        self.data.join("keys")
    }

    pub fn db_path(&self) -> PathBuf {
        self.data.join("hub.db")
    }

    /// The base URL without a trailing slash.
    pub fn base_url(&self) -> &str {
        self.server.base_url.trim_end_matches('/')
    }
}

fn parse_addr(s: &str) -> anyhow::Result<Option<SocketAddr>> {
    if s.trim().is_empty() {
        return Ok(None);
    }
    Ok(Some(s.parse().map_err(|e| anyhow::anyhow!("bind address {s:?}: {e}"))?))
}

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

    #[test]
    fn byte_sizes() {
        assert_eq!(ByteSize::parse("2MiB"), Some(ByteSize(2 << 20)));
        assert_eq!(ByteSize::parse("512"), Some(ByteSize(512)));
        assert_eq!(ByteSize::parse("4 GiB"), Some(ByteSize(4 << 30)));
        assert_eq!(ByteSize::parse("100kB"), Some(ByteSize(100_000)));
        assert_eq!(ByteSize::parse("lots"), None);
    }

    #[test]
    fn file_then_environment() {
        let mut cfg = Config::parse("[server]\nbind = \"0.0.0.0:7300\"\n[limits]\nrender_limit = \"1MiB\"\n").unwrap();
        assert_eq!(cfg.server.bind, "0.0.0.0:7300");
        assert_eq!(cfg.limits.render_limit, ByteSize(1 << 20));
        assert_eq!(cfg.site.name, "Oxygenhub");
        cfg.apply_env(|k| match k {
            "OXYHUB_SITE_NAME" => Some("Earth".into()),
            "OXYHUB_AUTH_PUSH_TOKENS" => Some("a, b".into()),
            _ => None,
        });
        assert_eq!(cfg.site.name, "Earth");
        assert_eq!(cfg.auth.push_tokens, ["a", "b"]);
        assert!(Config::parse("[nope]\nx = 1\n").is_err(), "unknown sections are errors, not silence");
    }
}