//! Which hub and repository a command talks to, and with which token.
//!
//! Inside an Oxygen checkout, `oh` uses the checkout's remote (`origin`, or
//! the only one, or `--remote NAME`): its URL names the hub and the
//! repository, and its token and CA are the ones `oxy` pushes with.
//! Elsewhere, `--repo OWNER/NAME` with the hub from `--hub`, `OH_HUB` or
//! the one `oh auth login` saved.

use anyhow::{anyhow, bail, Context, Result};
use serde::{Deserialize, Serialize};
use std::collections::BTreeMap;
use std::path::{Path, PathBuf};

/// `~/.config/oh/config.toml`: tokens and CAs by hub, and the default hub.
#[derive(Debug, Default, Serialize, Deserialize)]
pub struct Config {
    #[serde(default)]
    pub default_hub: Option<String>,
    #[serde(default)]
    pub hosts: BTreeMap<String, Host>,
}

#[derive(Clone, Debug, Default, Serialize, Deserialize)]
pub struct Host {
    pub token: String,
    #[serde(default)]
    pub ca: Option<PathBuf>,
}

pub fn config_path() -> Result<PathBuf> {
    if let Some(p) = std::env::var_os("OH_CONFIG") {
        return Ok(PathBuf::from(p));
    }
    let base = match std::env::var_os("XDG_CONFIG_HOME") {
        Some(d) => PathBuf::from(d),
        None => PathBuf::from(std::env::var_os("HOME").context("HOME is not set")?).join(".config"),
    };
    Ok(base.join("oh").join("config.toml"))
}

impl Config {
    pub fn load() -> Result<Config> {
        let p = config_path()?;
        match std::fs::read_to_string(&p) {
            Ok(t) => toml::from_str(&t).with_context(|| format!("parse {}", p.display())),
            Err(e) if e.kind() == std::io::ErrorKind::NotFound => Ok(Config::default()),
            Err(e) => Err(e).with_context(|| format!("read {}", p.display())),
        }
    }

    /// Written owner-only: it holds tokens.
    pub fn save(&self) -> Result<()> {
        use std::io::Write;
        use std::os::unix::fs::OpenOptionsExt;
        let p = config_path()?;
        std::fs::create_dir_all(p.parent().unwrap())?;
        let tmp = p.with_extension("toml.tmp");
        let mut f = std::fs::OpenOptions::new().write(true).create(true).truncate(true).mode(0o600).open(&tmp)?;
        f.write_all(toml::to_string_pretty(self)?.as_bytes())?;
        f.sync_all()?;
        std::fs::rename(&tmp, &p)?;
        Ok(())
    }
}

/// A hub, and a repository on it when the command needs one.
#[derive(Clone, Debug)]
pub struct Target {
    /// `https://host:port`, no trailing slash.
    pub hub: String,
    pub token: Option<String>,
    pub ca: Option<PathBuf>,
    pub owner: String,
    pub name: String,
}

impl Target {
    pub fn repo(&self) -> Result<(&str, &str)> {
        if self.owner.is_empty() {
            bail!("no repository: run inside an Oxygen checkout, or give --repo OWNER/NAME");
        }
        Ok((&self.owner, &self.name))
    }

    /// `/repos/{owner}/{name}`.
    pub fn repo_path(&self) -> Result<String> {
        let (o, n) = self.repo()?;
        Ok(format!("/repos/{o}/{n}"))
    }
}

/// Split `https://host:port/owner/name` into the hub and the repository.
pub fn split_url(url: &str) -> Result<(String, String, String)> {
    let (scheme, rest) = url.split_once("://").ok_or_else(|| anyhow!("{url} is not a hub URL"))?;
    let mut parts = rest.trim_end_matches('/').splitn(2, '/');
    let host = parts.next().unwrap_or("");
    let path = parts.next().unwrap_or("");
    let segs: Vec<&str> = path.split('/').filter(|s| !s.is_empty()).collect();
    match segs.as_slice() {
        [o, n] => Ok((format!("{scheme}://{host}"), o.to_string(), n.trim_end_matches(".oxy").to_string())),
        _ => bail!("{url} does not name a repository as https://hub/OWNER/NAME"),
    }
}

pub struct Choice<'a> {
    pub repo: Option<&'a str>,
    pub hub: Option<&'a str>,
    pub remote: Option<&'a str>,
}

/// Resolve what to talk to from the flags, the checkout at `dir`, the
/// environment and the saved configuration.
pub fn resolve(choice: &Choice, dir: &Path, cfg: &Config) -> Result<Target> {
    let env_token = std::env::var("OH_TOKEN").ok().or_else(|| std::env::var("OXY_TOKEN").ok()).filter(|t| !t.is_empty());
    let env_ca = std::env::var_os("OXY_CA").map(PathBuf::from);
    let saved = |hub: &str| cfg.hosts.get(hub).cloned();
    if let Some(r) = choice.repo {
        let (owner, name) = r.split_once('/').ok_or_else(|| anyhow!("--repo takes OWNER/NAME"))?;
        let hub = choice
            .hub
            .map(String::from)
            .or_else(|| std::env::var("OH_HUB").ok())
            .or_else(|| cfg.default_hub.clone())
            .ok_or_else(|| anyhow!("which hub? give --hub URL, set OH_HUB, or run `oh auth login`"))?;
        let hub = hub.trim_end_matches('/').to_string();
        let host = saved(&hub).unwrap_or_default();
        return Ok(Target {
            token: env_token.or(Some(host.token).filter(|t| !t.is_empty())),
            ca: env_ca.or(host.ca),
            hub,
            owner: owner.into(),
            name: name.into(),
        });
    }
    // The checkout's remote.
    if let Ok(repo) = oxy_core::repo::Repo::open(dir) {
        let remotes = &repo.config.remotes;
        let name = match choice.remote {
            Some(n) => n.to_string(),
            None if remotes.contains_key("origin") => "origin".into(),
            None if remotes.len() == 1 => remotes.keys().next().unwrap().clone(),
            None if remotes.is_empty() => bail!("this checkout has no remote; give --repo OWNER/NAME"),
            None => bail!(
                "this checkout has several remotes ({}); choose one with --remote",
                remotes.keys().cloned().collect::<Vec<_>>().join(", ")
            ),
        };
        let url = remotes.get(&name).ok_or_else(|| anyhow!("no remote named {name}"))?;
        let (hub, owner, repo_name) = split_url(url)?;
        let host = saved(&hub).unwrap_or_default();
        let token = env_token.or_else(|| repo.config.remote_tokens.get(&name).cloned()).or(Some(host.token).filter(|t| !t.is_empty()));
        let ca = env_ca.or_else(|| repo.config.remote_cas.get(&name).map(PathBuf::from)).or(host.ca);
        return Ok(Target { hub, token, ca, owner, name: repo_name });
    }
    // No repository: commands that need only a hub.
    let hub = choice
        .hub
        .map(String::from)
        .or_else(|| std::env::var("OH_HUB").ok())
        .or_else(|| cfg.default_hub.clone())
        .ok_or_else(|| anyhow!("not in an Oxygen checkout: give --repo OWNER/NAME and --hub URL, or run `oh auth login`"))?;
    let hub = hub.trim_end_matches('/').to_string();
    let host = saved(&hub).unwrap_or_default();
    Ok(Target {
        token: env_token.or(Some(host.token).filter(|t| !t.is_empty())),
        ca: env_ca.or(host.ca),
        hub,
        owner: String::new(),
        name: String::new(),
    })
}

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

    #[test]
    fn remote_urls_name_the_hub_and_the_repository() {
        assert_eq!(
            split_url("https://earth.example:7343/andy/oxygen").unwrap(),
            ("https://earth.example:7343".into(), "andy".into(), "oxygen".into())
        );
        assert_eq!(split_url("http://127.0.0.1:9/a/b/").unwrap().2, "b");
        assert!(split_url("https://hub/only-owner").is_err());
        assert!(split_url("not a url").is_err());
    }
}