//! Oxygen Strata: repositories kept on cloud object storage (docs/stores.md).
//!
//! This crate gives `oxy` the stores that need an HTTP client and the
//! providers' signing: Amazon S3 (`s3://BUCKET/PREFIX`), Google Cloud
//! Storage (`gs://BUCKET/PREFIX`) and Azure Blob Storage
//! (`az://ACCOUNT/CONTAINER/PREFIX`), each as a [`Store`] over the
//! `object_store` crate. Credentials come from each provider's standard
//! places, with nothing oxy-specific to set up; a URL may carry settings
//! as query parameters (`?profile=work&region=eu-west-2`), which is where
//! `oxy remote add --profile` keeps them.
//!
//! [`register`] hands these stores to oxy-core's remote opener; a program
//! that links this crate calls it once at start.

mod aws;
mod azure;
mod gcp;
mod ini;

use futures::TryStreamExt;
use object_store::path::Path as ObjectPath;
use object_store::{
    GetOptions, ObjectStore, ObjectStoreExt, PutMode, PutOptions, PutPayload, UpdateVersion,
};
use oxy_core::strata::{check_key, Entry, Error, Result, Store, Version};
use std::collections::BTreeMap;
use std::future::Future;
use std::ops::Range;
use std::sync::{Arc, Mutex};

/// Make the cloud stores available to `oxy_core::protocol::open_remote`.
/// Safe to call more than once.
pub fn register() {
    // object_store's reqwest is built with rustls and no bundled crypto
    // provider; oxy links ring already, so that is the one to install.
    let _ = rustls::crypto::ring::default_provider().install_default();
    oxy_core::protocol::register_store_opener(open_url);
}

fn open_url(
    url: &str,
    _options: &oxy_core::protocol::RemoteOptions,
) -> Option<Result<Box<dyn Store>>> {
    let scheme = url.split_once("://")?.0;
    if !matches!(scheme, "s3" | "gs" | "az") {
        return None;
    }
    Some(CloudStore::open(url).map(|s| Box::new(s) as Box<dyn Store>))
}

/// A parsed store URL: `SCHEME://HOST/PATH?PARAMS`.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct StoreUrl {
    pub scheme: String,
    /// The bucket (S3, GCS) or the storage account (Azure).
    pub host: String,
    /// The path under the host, without leading or trailing slashes; for
    /// Azure the container is its first segment.
    pub path: String,
    pub params: BTreeMap<String, String>,
}

impl StoreUrl {
    pub fn parse(url: &str) -> Result<StoreUrl> {
        let bad = |why: &str| Error::Backend(format!("{url}: {why}"));
        let (scheme, rest) = url.split_once("://").ok_or_else(|| bad("not a URL"))?;
        let (rest, query) = match rest.split_once('?') {
            Some((r, q)) => (r, Some(q)),
            None => (rest, None),
        };
        let (host, path) = match rest.split_once('/') {
            Some((h, p)) => (h, p.trim_matches('/')),
            None => (rest, ""),
        };
        if host.is_empty() {
            return Err(bad("names no bucket"));
        }
        let mut params = BTreeMap::new();
        for pair in query.unwrap_or("").split('&').filter(|p| !p.is_empty()) {
            let (k, v) = pair.split_once('=').unwrap_or((pair, ""));
            params.insert(k.to_string(), percent_decode(v));
        }
        Ok(StoreUrl {
            scheme: scheme.to_string(),
            host: host.to_string(),
            path: path.to_string(),
            params,
        })
    }

    /// The URL without its parameters, for messages.
    pub fn plain(&self) -> String {
        if self.path.is_empty() {
            format!("{}://{}", self.scheme, self.host)
        } else {
            format!("{}://{}/{}", self.scheme, self.host, self.path)
        }
    }

    pub fn param(&self, name: &str) -> Option<&str> {
        self.params.get(name).map(String::as_str)
    }
}

fn percent_decode(s: &str) -> String {
    let bytes = s.as_bytes();
    let mut out = Vec::with_capacity(bytes.len());
    let mut i = 0;
    while i < bytes.len() {
        if bytes[i] == b'%' && i + 2 < bytes.len() {
            if let Ok(v) = u8::from_str_radix(&s[i + 1..i + 3], 16) {
                out.push(v);
                i += 3;
                continue;
            }
        }
        out.push(bytes[i]);
        i += 1;
    }
    String::from_utf8_lossy(&out).into_owned()
}

/// A store on a cloud provider: the provider's client, the prefix every
/// key goes under, and a runtime to run the client on.
pub struct CloudStore {
    inner: Arc<dyn ObjectStore>,
    prefix: String,
    name: String,
    hint: &'static str,
    runtime: tokio::runtime::Runtime,
    /// One call at a time: the runtime runs on the calling thread.
    turn: Mutex<()>,
}

impl CloudStore {
    /// Open the store a URL names. Nothing is sent yet: credentials are
    /// resolved here, but the bucket is first spoken to on the first call.
    pub fn open(url: &str) -> Result<CloudStore> {
        let parsed = StoreUrl::parse(url)?;
        let runtime = tokio::runtime::Builder::new_current_thread()
            .enable_all()
            .build()
            .map_err(|e| Error::Backend(format!("starting the HTTP runtime: {e}")))?;
        let (inner, prefix, hint): (Arc<dyn ObjectStore>, String, &'static str) =
            match parsed.scheme.as_str() {
                "s3" => (
                    Arc::new(aws::open(&parsed, &runtime)?),
                    parsed.path.clone(),
                    aws::HINT,
                ),
                "gs" => (
                    Arc::new(gcp::open(&parsed)?),
                    parsed.path.clone(),
                    gcp::HINT,
                ),
                "az" => {
                    let (store, prefix) = azure::open(&parsed)?;
                    (Arc::new(store), prefix, azure::HINT)
                }
                other => {
                    return Err(Error::Backend(format!(
                        "{url}: {other}:// is not a store oxy knows (s3://, gs://, az://, dir://)"
                    )))
                }
            };
        Ok(CloudStore {
            inner,
            prefix,
            name: parsed.plain(),
            hint,
            runtime,
            turn: Mutex::new(()),
        })
    }

    fn block<F: Future>(&self, f: F) -> F::Output {
        let _turn = self.turn.lock().unwrap_or_else(|p| p.into_inner());
        self.runtime.block_on(f)
    }

    fn path(&self, key: &str) -> Result<ObjectPath> {
        check_key(key)?;
        let full = if self.prefix.is_empty() {
            key.to_string()
        } else {
            format!("{}/{key}", self.prefix)
        };
        ObjectPath::parse(&full).map_err(|e| Error::Backend(format!("{full}: {e}")))
    }

    /// Our error for the provider's, with what to do next where it helps.
    fn map(&self, e: object_store::Error, key: &str) -> Error {
        use object_store::Error as E;
        match e {
            E::NotFound { .. } => Error::NotFound(key.to_string()),
            E::AlreadyExists { .. } => Error::Exists(key.to_string()),
            E::Precondition { .. } | E::NotModified { .. } => Error::Conflict(key.to_string()),
            other => {
                let text = other.to_string();
                let lower = text.to_ascii_lowercase();
                let advice = if lower.contains("403")
                    || lower.contains("accessdenied")
                    || lower.contains("forbidden")
                    || lower.contains("authorizationpermissionmismatch")
                {
                    format!(
                        ": access denied; the credentials in use may not do this on {}: {}",
                        self.name, self.hint
                    )
                } else if lower.contains("credential") || lower.contains("no valid credentials") {
                    format!(": no usable credentials: {}", self.hint)
                } else if lower.contains("nosuchbucket")
                    || lower.contains("bucketnotfound")
                    || lower.contains("containernotfound")
                {
                    format!(
                        ": {} does not exist, or the credentials cannot see it",
                        self.name
                    )
                } else if lower.contains("dns")
                    || lower.contains("connect")
                    || lower.contains("timed out")
                {
                    ": cannot reach the service; check the network, the endpoint and the region"
                        .to_string()
                } else {
                    String::new()
                };
                Error::Backend(format!("{}: {text}{advice}", self.name))
            }
        }
    }

    fn version_of(e_tag: Option<String>, version: Option<String>) -> Version {
        Version(format!(
            "{}\t{}",
            e_tag.unwrap_or_default(),
            version.unwrap_or_default()
        ))
    }

    fn update_version(v: &Version) -> UpdateVersion {
        let (e_tag, version) = v.0.split_once('\t').unwrap_or((v.0.as_str(), ""));
        UpdateVersion {
            e_tag: (!e_tag.is_empty()).then(|| e_tag.to_string()),
            version: (!version.is_empty()).then(|| version.to_string()),
        }
    }
}

impl Store for CloudStore {
    fn describe(&self) -> String {
        self.name.clone()
    }

    fn has(&self, key: &str) -> Result<bool> {
        let path = self.path(key)?;
        match self.block(self.inner.head(&path)) {
            Ok(_) => Ok(true),
            Err(object_store::Error::NotFound { .. }) => Ok(false),
            Err(e) => Err(self.map(e, key)),
        }
    }

    fn get(&self, key: &str) -> Result<Vec<u8>> {
        let path = self.path(key)?;
        self.block(async {
            let r = self.inner.get(&path).await?;
            r.bytes().await
        })
        .map(|b| b.to_vec())
        .map_err(|e| self.map(e, key))
    }

    fn get_range(&self, key: &str, range: Range<u64>) -> Result<Vec<u8>> {
        let path = self.path(key)?;
        if range.start > range.end {
            return Err(Error::Backend(format!(
                "{key}: bytes {}..{} is not a range",
                range.start, range.end
            )));
        }
        if range.is_empty() {
            return Ok(Vec::new());
        }
        let want = (range.end - range.start) as usize;
        let bytes = self
            .block(self.inner.get_range(&path, range.clone()))
            .map_err(|e| self.map(e, key))?;
        if bytes.len() != want {
            return Err(Error::Backend(format!(
                "{key}: bytes {}..{} asked, {} returned: the object is shorter",
                range.start,
                range.end,
                bytes.len()
            )));
        }
        Ok(bytes.to_vec())
    }

    fn put_new(&self, key: &str, bytes: &[u8]) -> Result<()> {
        let path = self.path(key)?;
        let opts = PutOptions {
            mode: PutMode::Create,
            ..Default::default()
        };
        self.block(
            self.inner
                .put_opts(&path, PutPayload::from(bytes.to_vec()), opts),
        )
        .map(|_| ())
        .map_err(|e| self.map(e, key))
    }

    fn list(&self, prefix: &str) -> Result<Vec<Entry>> {
        // Providers list by whole path segments; the asked prefix may end
        // mid-segment, so list its directory and filter here.
        let dir = prefix.rsplit_once('/').map(|(d, _)| d).unwrap_or("");
        let full_dir = match (self.prefix.as_str(), dir) {
            ("", "") => None,
            ("", d) => Some(d.to_string()),
            (p, "") => Some(p.to_string()),
            (p, d) => Some(format!("{p}/{d}")),
        };
        let full_dir = full_dir
            .map(|d| ObjectPath::parse(&d).map_err(|e| Error::Backend(format!("{d}: {e}"))))
            .transpose()?;
        let metas: Vec<object_store::ObjectMeta> = self
            .block(self.inner.list(full_dir.as_ref()).try_collect())
            .map_err(|e| self.map(e, prefix))?;
        let strip = if self.prefix.is_empty() {
            String::new()
        } else {
            format!("{}/", self.prefix)
        };
        let mut out: Vec<Entry> = metas
            .into_iter()
            .filter_map(|m| {
                let loc = m.location.to_string();
                let key = loc.strip_prefix(&strip)?;
                key.starts_with(prefix).then(|| Entry {
                    key: key.to_string(),
                    size: m.size,
                })
            })
            .collect();
        out.sort_by(|a, b| a.key.cmp(&b.key));
        Ok(out)
    }

    fn delete(&self, key: &str) -> Result<()> {
        let path = self.path(key)?;
        match self.block(self.inner.delete(&path)) {
            Ok(()) | Err(object_store::Error::NotFound { .. }) => Ok(()),
            Err(e) => Err(self.map(e, key)),
        }
    }

    fn read_ref(&self, key: &str) -> Result<Option<(Vec<u8>, Version)>> {
        let path = self.path(key)?;
        let got = self.block(async {
            let r = self.inner.get_opts(&path, GetOptions::default()).await?;
            let meta = r.meta.clone();
            let bytes = r.bytes().await?;
            Ok::<_, object_store::Error>((bytes, meta))
        });
        match got {
            Ok((bytes, meta)) => Ok(Some((
                bytes.to_vec(),
                Self::version_of(meta.e_tag, meta.version),
            ))),
            Err(object_store::Error::NotFound { .. }) => Ok(None),
            Err(e) => Err(self.map(e, key)),
        }
    }

    fn write_ref(&self, key: &str, bytes: &[u8], expected: Option<&Version>) -> Result<Version> {
        let path = self.path(key)?;
        let mode = match expected {
            None => PutMode::Create,
            Some(v) => PutMode::Update(Self::update_version(v)),
        };
        let opts = PutOptions {
            mode,
            ..Default::default()
        };
        let put = self
            .block(
                self.inner
                    .put_opts(&path, PutPayload::from(bytes.to_vec()), opts),
            )
            .map_err(|e| match self.map(e, key) {
                // A record that exists when none was expected is a lost
                // race too, not a misuse of put_new.
                Error::Exists(k) => Error::Conflict(k),
                other => other,
            })?;
        Ok(Self::version_of(put.e_tag, put.version))
    }
}

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

    #[test]
    fn urls_parse_with_their_parameters() {
        let u =
            StoreUrl::parse("s3://my-bucket/repos/oxygen?profile=work&region=eu-west-2").unwrap();
        assert_eq!(u.scheme, "s3");
        assert_eq!(u.host, "my-bucket");
        assert_eq!(u.path, "repos/oxygen");
        assert_eq!(u.param("profile"), Some("work"));
        assert_eq!(u.param("region"), Some("eu-west-2"));
        assert_eq!(u.plain(), "s3://my-bucket/repos/oxygen");
        let u = StoreUrl::parse("gs://bucket").unwrap();
        assert_eq!((u.host.as_str(), u.path.as_str()), ("bucket", ""));
        assert_eq!(u.plain(), "gs://bucket");
        let u = StoreUrl::parse("az://acct/container/a/b/?endpoint=http%3A%2F%2F127.0.0.1%3A10000")
            .unwrap();
        assert_eq!(u.path, "container/a/b");
        assert_eq!(u.param("endpoint"), Some("http://127.0.0.1:10000"));
        assert!(StoreUrl::parse("s3://").is_err());
        assert!(StoreUrl::parse("nonsense").is_err());
    }

    #[test]
    fn versions_carry_both_an_etag_and_a_generation() {
        let v = CloudStore::version_of(Some("\"abc\"".into()), Some("17".into()));
        let u = CloudStore::update_version(&v);
        assert_eq!(u.e_tag.as_deref(), Some("\"abc\""));
        assert_eq!(u.version.as_deref(), Some("17"));
        let u = CloudStore::update_version(&CloudStore::version_of(None, Some("3".into())));
        assert_eq!((u.e_tag, u.version.as_deref()), (None, Some("3")));
    }
}