//! Runtime configuration, loaded from an external file — nothing here is compiled into the binary.
//!
//! Precedence: environment variables override the file, the file overrides built-in defaults. On
//! first run, if the file is absent, a default one is written with a freshly generated auth token,
//! so the sidecar is secured out of the box and the operator just copies the token to the website.
//!
//! File path: `--config <PATH>`, else `$UOLINK_CONFIG`, else `sidecar.toml` in the working
//! directory.
//!
//! **Paths are anchored to the config file, not the working directory.** A relative
//! `[store].path` resolves against the directory holding `sidecar.toml`. A service started with
//! `UOLINK_CONFIG=/etc/runicgateway/sidecar.toml` therefore keeps its database beside its config
//! instead of wherever the service manager happened to set the working directory — which on
//! Windows can be `%SystemRoot%\System32` or, under `C:\Program Files\`, a silently redirected
//! VirtualStore copy. The values reported by `--print-config` are the resolved absolute ones.

use std::env;
use std::fs;
use std::path::{Component, Path, PathBuf};

use serde::Deserialize;
use serde_json::json;
use tracing::info;

use crate::PROTOCOL_VERSION;

#[derive(Debug, Default, Deserialize)]
pub struct Config {
    #[serde(default)]
    pub shard: ShardCfg,
    #[serde(default)]
    pub web: WebCfg,
    #[serde(default)]
    pub store: StoreCfg,
}

#[derive(Debug, Deserialize)]
pub struct ShardCfg {
    #[serde(default = "default_shard_bind")]
    pub bind: String,
}

#[derive(Debug, Deserialize)]
pub struct WebCfg {
    #[serde(default = "default_web_bind")]
    pub bind: String,
    /// Shared secret the website must present. Never empty in practice — `Config::load` generates
    /// and persists one when it finds none, so the web surface is authenticated from first boot.
    #[serde(default)]
    pub auth_token: String,
}

#[derive(Debug, Deserialize)]
pub struct StoreCfg {
    #[serde(default = "default_db_path")]
    pub path: String,
}

/// A loaded configuration plus what loading it *did* — an installer re-running the binary needs to
/// distinguish "read an existing install" from "provisioned a new one", and it cannot tell from the
/// values alone.
#[derive(Debug)]
pub struct Loaded {
    pub cfg: Config,
    /// Absolute path of the config file that was read or written.
    pub path: PathBuf,
    /// The config file did not exist and was created by this run.
    pub config_created: bool,
    /// No usable token was configured, so one was generated and saved.
    pub token_generated: bool,
}

fn default_shard_bind() -> String {
    "127.0.0.1:7788".into()
}
fn default_web_bind() -> String {
    "127.0.0.1:8080".into()
}
fn default_db_path() -> String {
    "uo-link.db".into()
}

impl Default for ShardCfg {
    fn default() -> Self {
        Self {
            bind: default_shard_bind(),
        }
    }
}
impl Default for WebCfg {
    fn default() -> Self {
        Self {
            bind: default_web_bind(),
            auth_token: String::new(),
        }
    }
}
impl Default for StoreCfg {
    fn default() -> Self {
        Self {
            path: default_db_path(),
        }
    }
}

impl Config {
    /// Which config file this invocation will use: `--config`, else `$UOLINK_CONFIG`, else
    /// `sidecar.toml` beside the working directory. Always returned absolute, so every later
    /// message names a path the operator can act on.
    pub fn resolve_path(cli_override: Option<&str>) -> PathBuf {
        let raw = cli_override
            .map(str::to_string)
            .or_else(|| env::var("UOLINK_CONFIG").ok())
            .unwrap_or_else(|| "sidecar.toml".into());
        absolutize(PathBuf::from(raw))
    }

    pub fn load(cli_override: Option<&str>) -> anyhow::Result<Loaded> {
        let path = Self::resolve_path(cli_override);
        let existed = path.exists();

        let mut cfg: Config = if existed {
            let text = fs::read_to_string(&path)?;
            toml::from_str(&text)?
        } else {
            Config::default()
        };

        cfg.apply_env();

        // Authentication is always on. A blank token is never allowed — if none is set (fresh
        // install, or someone cleared it), generate one, save it, and continue. This keeps setup
        // effortless while making it impossible to accidentally run with auth off.
        let token_generated = cfg.web.auth_token.trim().is_empty();
        if token_generated {
            let token = generate_token();

            if existed {
                persist_token(&path, &token)?;
            } else {
                // The parent may not exist yet when an installer points at a fresh
                // /etc/runicgateway; failing here would mean "run me again after mkdir".
                create_parent_dir(&path)?;
                fs::write(&path, default_file(&token))?;
            }

            cfg.web.auth_token = token.clone();

            info!("No auth token configured.");
            info!("Generated new token: {}", token);
            info!("Saved to {}. Authentication is on.", path.display());
        }

        cfg.anchor_store_path(&path);

        Ok(Loaded {
            cfg,
            path,
            config_created: !existed,
            token_generated,
        })
    }

    /// Environment overrides, so a deployment can set secrets without editing the file.
    fn apply_env(&mut self) {
        if let Ok(v) = env::var("UOLINK_SHARD_BIND") {
            self.shard.bind = v;
        }
        if let Ok(v) = env::var("UOLINK_WEB_BIND") {
            self.web.bind = v;
        }
        if let Ok(v) = env::var("UOLINK_WEB_TOKEN") {
            self.web.auth_token = v;
        }
        if let Ok(v) = env::var("UOLINK_DB_PATH") {
            self.store.path = v;
        }
    }

    /// Resolves `[store].path` against the config file's directory (see the module docs). Absolute
    /// paths and SQLite's non-filesystem spellings are left exactly as written.
    fn anchor_store_path(&mut self, config_path: &Path) {
        if is_sqlite_special(&self.store.path) {
            return;
        }
        let raw = PathBuf::from(&self.store.path);
        let anchored = if raw.is_absolute() {
            raw
        } else {
            config_dir(config_path).join(raw)
        };
        self.store.path = absolutize(anchored).to_string_lossy().into_owned();
    }

    pub fn auth_required(&self) -> bool {
        // Always true now — load() guarantees a non-empty token.
        !self.web.auth_token.is_empty()
    }
}

/// The `--print-config` document: everything an installer needs to register this sidecar with a
/// website, in one non-interactive read.
///
/// **This includes the auth token in clear text**, which is the point — §2.4 of the installer plan
/// calls the manual token hunt the largest "I installed it and nothing happened" failure mode. The
/// caller prints it to stdout and starts no log subscriber, so the document is the whole output.
pub fn describe(loaded: &Loaded) -> serde_json::Value {
    json!({
        "component": "uo-link-sidecar",
        "version": env!("CARGO_PKG_VERSION"),
        "protocol": PROTOCOL_VERSION,
        "config_path": loaded.path.to_string_lossy(),
        "config_created": loaded.config_created,
        "token_generated": loaded.token_generated,
        "shard": { "bind": loaded.cfg.shard.bind },
        "web": {
            "bind": loaded.cfg.web.bind,
            "ws_path": crate::web::WS_PATH,
            "auth_required": loaded.cfg.auth_required(),
            "auth_token": loaded.cfg.web.auth_token,
        },
        "store": { "path": loaded.cfg.store.path },
    })
}

/// Directory holding the config file. A bare `sidecar.toml` has no parent component, which would
/// join into an empty base — treat it as the current directory.
fn config_dir(config_path: &Path) -> PathBuf {
    match config_path.parent() {
        Some(p) if !p.as_os_str().is_empty() => p.to_path_buf(),
        _ => PathBuf::from("."),
    }
}

/// Prefixes the working directory onto a relative path, then drops the `.` components that
/// joining leaves behind — cosmetic, but these paths are printed and pasted into service units.
fn absolutize(p: PathBuf) -> PathBuf {
    let joined = if p.is_absolute() {
        p
    } else {
        match env::current_dir() {
            Ok(cwd) => cwd.join(p),
            Err(_) => p,
        }
    };
    let cleaned: PathBuf = joined
        .components()
        .filter(|c| !matches!(c, Component::CurDir))
        .collect();
    if cleaned.as_os_str().is_empty() {
        joined
    } else {
        cleaned
    }
}

/// `:memory:` and `file:` URIs are instructions to SQLite, not paths on disk. Anchoring them to a
/// directory would turn a working in-memory store into an attempt to create a file called
/// `:memory:` — which Windows cannot even name.
fn is_sqlite_special(path: &str) -> bool {
    path == ":memory:" || path.starts_with("file:")
}

fn create_parent_dir(path: &Path) -> anyhow::Result<()> {
    if let Some(dir) = path.parent() {
        if !dir.as_os_str().is_empty() && !dir.exists() {
            fs::create_dir_all(dir)?;
        }
    }
    Ok(())
}

/// Rewrites the `auth_token` line in an existing config file, preserving everything else. Falls
/// back to inserting it under `[web]`, or appending a `[web]` section, if the key is absent.
fn persist_token(path: &Path, token: &str) -> anyhow::Result<()> {
    let text = fs::read_to_string(path)?;
    let line = format!("auth_token = \"{token}\"");

    if text
        .lines()
        .any(|l| l.trim_start().starts_with("auth_token"))
    {
        let out: String = text
            .lines()
            .map(|l| {
                if l.trim_start().starts_with("auth_token") {
                    line.clone()
                } else {
                    l.to_string()
                }
            })
            .collect::<Vec<_>>()
            .join("\n");
        fs::write(path, out + "\n")?;
    } else if text.lines().any(|l| l.trim() == "[web]") {
        let out: String = text
            .lines()
            .flat_map(|l| {
                if l.trim() == "[web]" {
                    vec![l.to_string(), line.clone()]
                } else {
                    vec![l.to_string()]
                }
            })
            .collect::<Vec<_>>()
            .join("\n");
        fs::write(path, out + "\n")?;
    } else {
        fs::write(path, format!("{text}\n[web]\n{line}\n"))?;
    }

    Ok(())
}

fn generate_token() -> String {
    let mut buf = [0u8; 24];
    // OS randomness; falls back to a time-seeded token only if the OS RNG is unavailable.
    if getrandom::getrandom(&mut buf).is_err() {
        let nanos = std::time::SystemTime::now()
            .duration_since(std::time::UNIX_EPOCH)
            .map(|d| d.as_nanos())
            .unwrap_or(0);
        return format!("insecure-fallback-{nanos:x}");
    }
    buf.iter().map(|b| format!("{b:02x}")).collect()
}

fn default_file(token: &str) -> String {
    format!(
        r#"# uo-link sidecar configuration.
# Read at startup. Nothing here is compiled into the binary. Environment variables
# (UOLINK_SHARD_BIND, UOLINK_WEB_BIND, UOLINK_WEB_TOKEN, UOLINK_DB_PATH) override these.

[shard]
# Loopback address the shard dials out to. Keep this on localhost — the game must
# not be reachable from anywhere else.
bind = "127.0.0.1:7788"

[web]
# Address the website connects to (WebSocket + REST).
#   127.0.0.1:8080  -> same host only
#   0.0.0.0:8080    -> accept remote clients (then auth_token is mandatory)
bind = "127.0.0.1:8080"

# Shared secret the website must present on every request:
#   REST:      Authorization: Bearer <token>     (or  X-Api-Key: <token>)
#   WebSocket: add  ?token=<token>  to the connect URL
# Authentication is always on: if this is left blank, the sidecar generates a new
# token here on startup. Rotate by changing this value and restarting.
# Read it back without starting the sidecar:  uo-link-sidecar --print-config
auth_token = "{token}"

[store]
# Relative paths resolve against the directory holding THIS FILE, not the working
# directory of the process.
path = "uo-link.db"
"#
    )
}

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

    /// A unique scratch directory. `std::env::temp_dir()` plus the test name keeps the cases
    /// independent under the default parallel test runner.
    fn scratch(name: &str) -> PathBuf {
        let dir = env::temp_dir().join(format!("uo-link-cfg-test-{name}"));
        let _ = fs::remove_dir_all(&dir);
        fs::create_dir_all(&dir).expect("create scratch dir");
        dir
    }

    /// `Config::load` consults the process environment, and a developer may have `UOLINK_*` set
    /// for a local shard. Mutating shared env state from a test thread is worse than skipping, so
    /// the two cases that exercise the full load path bail out instead of failing spuriously.
    fn env_overrides_present() -> bool {
        [
            "UOLINK_SHARD_BIND",
            "UOLINK_WEB_BIND",
            "UOLINK_WEB_TOKEN",
            "UOLINK_DB_PATH",
        ]
        .iter()
        .any(|k| env::var_os(k).is_some())
    }

    fn cfg_with_store(path: &str) -> Config {
        Config {
            store: StoreCfg { path: path.into() },
            ..Default::default()
        }
    }

    #[test]
    fn relative_store_path_anchors_to_the_config_directory() {
        // The working-directory trap: the service pins UOLINK_CONFIG but the service manager
        // decides the CWD, so a relative db path must not follow the CWD.
        let mut cfg = cfg_with_store("uo-link.db");
        let config_path = if cfg!(windows) {
            PathBuf::from(r"C:\ProgramData\RunicGateway\sidecar.toml")
        } else {
            PathBuf::from("/etc/runicgateway/sidecar.toml")
        };
        cfg.anchor_store_path(&config_path);

        let expected = config_path.parent().unwrap().join("uo-link.db");
        assert_eq!(Path::new(&cfg.store.path), expected);
    }

    #[test]
    fn absolute_store_path_is_left_alone() {
        let absolute = if cfg!(windows) {
            r"C:\ProgramData\RunicGateway\uo-link.db"
        } else {
            "/var/lib/runicgateway/uo-link.db"
        };
        let mut cfg = cfg_with_store(absolute);
        cfg.anchor_store_path(Path::new("/etc/runicgateway/sidecar.toml"));
        assert_eq!(cfg.store.path, absolute);
    }

    #[test]
    fn a_bare_config_filename_anchors_to_the_working_directory() {
        // `cargo run` in the crate root: config dir and CWD are the same, so the historical
        // behavior (db beside the binary's CWD) is preserved exactly.
        let mut cfg = cfg_with_store("uo-link.db");
        cfg.anchor_store_path(Path::new("sidecar.toml"));
        assert_eq!(
            Path::new(&cfg.store.path),
            env::current_dir().unwrap().join("uo-link.db")
        );
    }

    #[test]
    fn sqlite_special_paths_are_not_anchored() {
        for special in [":memory:", "file:cache?mode=memory"] {
            let mut cfg = cfg_with_store(special);
            cfg.anchor_store_path(Path::new("/etc/runicgateway/sidecar.toml"));
            assert_eq!(cfg.store.path, special);
        }
    }

    #[test]
    fn resolve_path_prefers_the_cli_override() {
        // Absolute in, absolute out — and unchanged, so the operator sees the path they passed.
        let explicit = if cfg!(windows) {
            r"C:\tmp\custom.toml"
        } else {
            "/tmp/custom.toml"
        };
        assert_eq!(
            Config::resolve_path(Some(explicit)),
            PathBuf::from(explicit)
        );
    }

    #[test]
    fn resolve_path_makes_a_relative_override_absolute() {
        let resolved = Config::resolve_path(Some("./conf/sidecar.toml"));
        assert!(resolved.is_absolute(), "{}", resolved.display());
        assert_eq!(
            resolved,
            env::current_dir()
                .unwrap()
                .join("conf")
                .join("sidecar.toml")
        );
    }

    #[test]
    fn persist_token_replaces_an_existing_key() {
        let dir = scratch("replace");
        let path = dir.join("sidecar.toml");
        fs::write(
            &path,
            "[web]\nbind = \"127.0.0.1:8080\"\nauth_token = \"\"\n\n[store]\npath = \"x.db\"\n",
        )
        .unwrap();

        persist_token(&path, "deadbeef").unwrap();

        let out = fs::read_to_string(&path).unwrap();
        assert!(out.contains("auth_token = \"deadbeef\""), "{out}");
        assert_eq!(out.matches("auth_token").count(), 1, "{out}");
        // Everything else survives — the file is the operator's, not ours to rewrite.
        assert!(out.contains("bind = \"127.0.0.1:8080\""), "{out}");
        assert!(out.contains("path = \"x.db\""), "{out}");
    }

    #[test]
    fn persist_token_inserts_under_an_existing_web_section() {
        let dir = scratch("insert");
        let path = dir.join("sidecar.toml");
        fs::write(&path, "[web]\nbind = \"127.0.0.1:8080\"\n").unwrap();

        persist_token(&path, "deadbeef").unwrap();

        let out = fs::read_to_string(&path).unwrap();
        let web = out.find("[web]").unwrap();
        let token = out.find("auth_token").unwrap();
        assert!(token > web, "token must land inside [web]: {out}");
        assert!(out.contains("auth_token = \"deadbeef\""), "{out}");
    }

    #[test]
    fn persist_token_appends_a_web_section_when_there_is_none() {
        let dir = scratch("append");
        let path = dir.join("sidecar.toml");
        fs::write(&path, "[shard]\nbind = \"127.0.0.1:7788\"\n").unwrap();

        persist_token(&path, "deadbeef").unwrap();

        let out = fs::read_to_string(&path).unwrap();
        assert!(out.contains("[shard]"), "{out}");
        assert!(out.contains("[web]\nauth_token = \"deadbeef\""), "{out}");
    }

    #[test]
    fn a_generated_config_round_trips_through_the_parser() {
        // The template is a format! string, so a stray brace or a bad key would only ever surface
        // on someone's first run.
        let cfg: Config = toml::from_str(&default_file("deadbeef")).expect("template parses");
        assert_eq!(cfg.web.auth_token, "deadbeef");
        assert_eq!(cfg.shard.bind, "127.0.0.1:7788");
        assert_eq!(cfg.web.bind, "127.0.0.1:8080");
        assert_eq!(cfg.store.path, "uo-link.db");
    }

    #[test]
    fn generated_tokens_are_random_and_hex() {
        let (a, b) = (generate_token(), generate_token());
        assert_ne!(a, b);
        assert_eq!(a.len(), 48);
        assert!(a.chars().all(|c| c.is_ascii_hexdigit()), "{a}");
    }

    #[test]
    fn describe_reports_the_resolved_configuration() {
        let loaded = Loaded {
            cfg: Config {
                shard: ShardCfg {
                    bind: "127.0.0.1:7788".into(),
                },
                web: WebCfg {
                    bind: "0.0.0.0:8080".into(),
                    auth_token: "deadbeef".into(),
                },
                store: StoreCfg {
                    path: "/var/lib/runicgateway/uo-link.db".into(),
                },
            },
            path: PathBuf::from("/etc/runicgateway/sidecar.toml"),
            config_created: true,
            token_generated: true,
        };

        let doc = describe(&loaded);

        assert_eq!(doc["component"], "uo-link-sidecar");
        assert_eq!(doc["version"], env!("CARGO_PKG_VERSION"));
        assert_eq!(doc["protocol"], PROTOCOL_VERSION);
        assert_eq!(doc["config_path"], "/etc/runicgateway/sidecar.toml");
        assert_eq!(doc["config_created"], true);
        assert_eq!(doc["token_generated"], true);
        assert_eq!(doc["shard"]["bind"], "127.0.0.1:7788");
        assert_eq!(doc["web"]["bind"], "0.0.0.0:8080");
        assert_eq!(doc["web"]["ws_path"], "/ws");
        assert_eq!(doc["web"]["auth_required"], true);
        assert_eq!(doc["web"]["auth_token"], "deadbeef");
        assert_eq!(doc["store"]["path"], "/var/lib/runicgateway/uo-link.db");
    }

    #[test]
    fn load_provisions_a_missing_config_and_reports_it() {
        if env_overrides_present() {
            return;
        }
        let dir = scratch("provision");
        let path = dir.join("sidecar.toml");

        let loaded = Config::load(Some(path.to_str().unwrap())).unwrap();

        assert!(loaded.config_created);
        assert!(loaded.token_generated);
        assert!(
            path.exists(),
            "the config file must be written, not just held in memory"
        );
        assert!(!loaded.cfg.web.auth_token.is_empty());
        // The db lands beside the config, whatever the working directory is.
        assert_eq!(Path::new(&loaded.cfg.store.path), dir.join("uo-link.db"));

        // Second run: same token, and nothing reported as new.
        let again = Config::load(Some(path.to_str().unwrap())).unwrap();
        assert!(!again.config_created);
        assert!(!again.token_generated);
        assert_eq!(again.cfg.web.auth_token, loaded.cfg.web.auth_token);
    }

    #[test]
    fn load_creates_the_config_directory() {
        if env_overrides_present() {
            return;
        }
        // An installer pointing at a fresh /etc/runicgateway should not have to mkdir first.
        let dir = scratch("mkdir").join("nested").join("deeper");
        let path = dir.join("sidecar.toml");

        let loaded = Config::load(Some(path.to_str().unwrap())).unwrap();

        assert!(path.exists(), "{}", path.display());
        assert!(loaded.config_created);
    }
}