//! Generic, authorized reads of live data declared in content
//! (`content::ResourceSpec`, on a `Feature`). The one property that
//! matters: what a resource reads is never a client-supplied parameter,
//! only something the server resolves from its own trusted, YAML-loaded
//! content - the client only ever names a question id + feature name
//! (plus, now, whatever form-field values it already has, forwarded as
//! query params), never a bucket/URL directly.

use leptos::prelude::*;

/// Fetches the live data for `question_id`'s `alternative`'s
/// `feature_name` feature. Fails closed: a resource with neither
/// `public: true` nor `requires_group` set is unreachable, not "open"
/// by omission. `params` are the requesting form's current field
/// values (if any) - forwarded as query parameters to a live external
/// fetch (`GiteaStarred`/`GiteaOrgRepos`/`Url`), the mechanism behind
/// "a resource parameterized by other form fields"; a `Kv` resource
/// ignores them entirely, same as today.
#[server]
pub async fn get_resource(
    question_id: String,
    alternative: String,
    feature_name: String,
    params: std::collections::HashMap<String, String>,
) -> Result<serde_json::Value, ServerFnError> {
    use crate::auth::{User, SESSION_USER_KEY};
    use crate::content::ResourceSource;
    use crate::server::AppState;

    let state = expect_context::<AppState>();
    let question = state
        .questions
        .load()
        .get(&question_id)
        .cloned()
        .ok_or_else(|| ServerFnError::new("unknown question"))?;
    // Scoped to the named alternative first, not flattened across all
    // of them - a feature name (often just "") is only unique within
    // its own alternative, not across a whole question. Flattening
    // silently resolved every same-named feature to whichever
    // alternative happened to be first, so "Subscribers" (and any
    // other later resource-listing alternative sharing an unnamed
    // feature with an earlier one on the same question) always read
    // the first alternative's bucket instead of its own.
    let feature = question
        .alternatives
        .iter()
        .find(|a| a.name == alternative)
        .ok_or_else(|| ServerFnError::new("unknown alternative"))?
        .features
        .iter()
        .find(|f| f.name == feature_name)
        .ok_or_else(|| ServerFnError::new("unknown feature"))?;
    let resource = feature
        .resource
        .as_ref()
        .ok_or_else(|| ServerFnError::new("feature has no resource"))?;

    if !resource.public {
        let group = resource
            .requires_group
            .as_deref()
            .ok_or_else(|| ServerFnError::new("resource is not accessible"))?;
        let session: tower_sessions::Session = leptos_axum::extract().await?;
        let user = session
            .get::<User>(SESSION_USER_KEY)
            .await
            .map_err(|e| ServerFnError::new(e.to_string()))?
            .ok_or_else(|| ServerFnError::new("not signed in"))?;
        if !user.groups.iter().any(|g| g == group) {
            return Err(ServerFnError::new("not authorized"));
        }
    }

    let value = match &resource.source {
        ResourceSource::Kv { bucket } => {
            let store = state
                .jetstream
                .get_key_value(bucket)
                .await
                .map_err(|e| ServerFnError::new(format!("resource bucket unavailable: {e}")))?;
            match &resource.key {
                Some(key) => {
                    let bytes = store
                        .get(key)
                        .await
                        .map_err(|e| ServerFnError::new(e.to_string()))?
                        .ok_or_else(|| ServerFnError::new("resource key not found"))?;
                    serde_json::from_slice(&bytes).map_err(|e| ServerFnError::new(e.to_string()))?
                }
                None => {
                    use futures::TryStreamExt;
                    let keys: Vec<String> = store
                        .keys()
                        .await
                        .map_err(|e| ServerFnError::new(e.to_string()))?
                        .try_collect()
                        .await
                        .map_err(|e| ServerFnError::new(e.to_string()))?;
                    let mut items = Vec::new();
                    for key in keys {
                        if let Ok(Some(bytes)) = store.get(&key).await {
                            if let Ok(value) = serde_json::from_slice::<serde_json::Value>(&bytes) {
                                items.push(value);
                            }
                        }
                    }
                    serde_json::Value::Array(items)
                }
            }
        }
        ResourceSource::GiteaStarred { username } => {
            fetch_gitea_json(&state, &format!("/api/v1/users/{username}/starred"), &params).await?
        }
        ResourceSource::GiteaOrgRepos { org } => {
            fetch_gitea_json(&state, &format!("/api/v1/orgs/{org}/repos"), &params).await?
        }
        ResourceSource::Url { url } => fetch_url_json(url, &params).await?,
    };

    match &resource.jq {
        Some(filter) => apply_jq(filter, &value),
        None => Ok(value),
    }
}

/// Fetches JSON from a path on the same Gitea instance content is
/// loaded from (`AppState.gitea_base`), attaching `GITEA_API_TOKEN` if
/// set - confirmed live against `project.uhhm.no` that at least the
/// starred-repos endpoint 401s unauthenticated, unlike the repo
/// -contents/repo-info endpoints `content.rs` already calls anonymously.
#[cfg(feature = "ssr")]
async fn fetch_gitea_json(
    state: &crate::server::AppState,
    path: &str,
    params: &std::collections::HashMap<String, String>,
) -> Result<serde_json::Value, ServerFnError> {
    let mut url = url::Url::parse(&format!("{}{}", state.gitea_base, path))
        .map_err(|e| ServerFnError::new(e.to_string()))?;
    for (k, v) in params {
        url.query_pairs_mut().append_pair(k, v);
    }
    let client = openidconnect::reqwest::Client::new();
    let mut req = client.get(url.clone());
    if let Ok(token) = std::env::var("GITEA_API_TOKEN") {
        if !token.is_empty() {
            req = req.header("Authorization", format!("token {token}"));
        }
    }
    let text = req
        .send()
        .await
        .and_then(|r| r.error_for_status())
        .map_err(|e| ServerFnError::new(format!("fetching {url}: {e}")))?
        .text()
        .await
        .map_err(|e| ServerFnError::new(e.to_string()))?;
    serde_json::from_str(&text).map_err(|e| ServerFnError::new(e.to_string()))
}

/// Fetches JSON from an arbitrary content-declared URL
/// (`content::ResourceSource::Url`). Content is trusted today (same
/// org owns both this app and its content repo), but a server-side
/// fetch of a content-supplied URL is real SSRF surface the moment
/// that stops being true - `assert_public_https_url` fails closed on
/// anything that isn't `https://` and actually resolves to a public
/// address, not just a syntactically-plausible one.
#[cfg(feature = "ssr")]
async fn fetch_url_json(
    url: &str,
    params: &std::collections::HashMap<String, String>,
) -> Result<serde_json::Value, ServerFnError> {
    let mut parsed = assert_public_https_url(url)
        .await
        .map_err(|e| ServerFnError::new(e.to_string()))?;
    for (k, v) in params {
        parsed.query_pairs_mut().append_pair(k, v);
    }
    let client = openidconnect::reqwest::Client::new();
    let text = client
        .get(parsed.clone())
        .send()
        .await
        .and_then(|r| r.error_for_status())
        .map_err(|e| ServerFnError::new(format!("fetching {parsed}: {e}")))?
        .text()
        .await
        .map_err(|e| ServerFnError::new(e.to_string()))?;
    serde_json::from_str(&text).map_err(|e| ServerFnError::new(e.to_string()))
}

/// `https://` only, and only if every address the host resolves to is
/// public - rejects loopback (127.0.0.1, ::1), RFC1918/link-local
/// private ranges, and unspecified/multicast addresses. Resolves via
/// real DNS (not just a syntax check) so a hostname that *points at* an
/// internal address is caught too, not just a literal internal IP
/// spelled out directly.
#[cfg(feature = "ssr")]
async fn assert_public_https_url(url: &str) -> anyhow::Result<url::Url> {
    let parsed = url::Url::parse(url)?;
    if parsed.scheme() != "https" {
        anyhow::bail!("only https:// resource urls are allowed");
    }
    let host = parsed
        .host_str()
        .ok_or_else(|| anyhow::anyhow!("resource url has no host"))?;
    let port = parsed.port_or_known_default().unwrap_or(443);
    let mut resolved = false;
    for addr in tokio::net::lookup_host((host, port))
        .await
        .map_err(|e| anyhow::anyhow!("resolving resource host {host}: {e}"))?
    {
        resolved = true;
        if !is_public_ip(&addr.ip()) {
            anyhow::bail!("resource host {host} resolves to a non-public address");
        }
    }
    if !resolved {
        anyhow::bail!("resource host {host} did not resolve to any address");
    }
    Ok(parsed)
}

#[cfg(feature = "ssr")]
fn is_public_ip(ip: &std::net::IpAddr) -> bool {
    match ip {
        std::net::IpAddr::V4(v4) => {
            !(v4.is_private()
                || v4.is_loopback()
                || v4.is_link_local()
                || v4.is_multicast()
                || v4.is_broadcast()
                || v4.is_unspecified()
                || v4.is_documentation())
        }
        std::net::IpAddr::V6(v6) => {
            let is_unique_local = (v6.segments()[0] & 0xfe00) == 0xfc00;
            let is_link_local = (v6.segments()[0] & 0xffc0) == 0xfe80;
            !(v6.is_loopback()
                || v6.is_unspecified()
                || v6.is_multicast()
                || is_unique_local
                || is_link_local)
        }
    }
}

/// Runs `filter_src` (a jq filter) over `input`, collecting every value
/// it yields into a JSON array - e.g. `.[] | {name, url: .html_url}`
/// over a Gitea repo list yields one shaped object per repo. Pure Rust
/// via the `jaq` crate family, no shell-out to a `jq` binary.
#[cfg(feature = "ssr")]
pub fn apply_jq(
    filter_src: &str,
    input: &serde_json::Value,
) -> Result<serde_json::Value, ServerFnError> {
    use jaq_core::load::{Arena, File, Loader};
    use jaq_core::{data, unwrap_valr, Compiler, Ctx, Vars};
    use jaq_json::{read, Val};

    let input_text = input.to_string();
    let input_val = read::parse_single(input_text.as_bytes())
        .map_err(|e| ServerFnError::new(format!("internal: re-parsing json for jq: {e:?}")))?;

    let program = File { code: filter_src, path: () };
    let defs = jaq_core::defs().chain(jaq_std::defs()).chain(jaq_json::defs());
    let funs = jaq_core::funs().chain(jaq_std::funs()).chain(jaq_json::funs());
    let loader = Loader::new(defs);
    let arena = Arena::default();
    let modules = loader
        .load(&arena, program)
        .map_err(|e| ServerFnError::new(format!("jq filter parse error: {e:?}")))?;
    let filter = Compiler::default()
        .with_funs(funs)
        .compile(modules)
        .map_err(|e| ServerFnError::new(format!("jq filter compile error: {e:?}")))?;
    let ctx = Ctx::<data::JustLut<Val>>::new(&filter.lut, Vars::new([]));

    let mut outputs = Vec::new();
    for result in filter.id.run((ctx, input_val)).map(unwrap_valr) {
        let val = result.map_err(|e| ServerFnError::new(format!("jq filter runtime error: {e:?}")))?;
        let text = val.to_string();
        let json: serde_json::Value = serde_json::from_str(&text)
            .map_err(|e| ServerFnError::new(format!("internal: parsing jq output: {e}")))?;
        outputs.push(json);
    }
    Ok(serde_json::Value::Array(outputs))
}

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

    /// A canned, Gitea-API-shaped fixture - the same fields the real
    /// `/users/{username}/starred` endpoint returns - run through the
    /// filter `index.yaml`'s "What we've built" resource actually
    /// declares, confirming the `jaq` integration produces the shape
    /// the frontend showcase card expects.
    #[test]
    fn jq_shapes_gitea_repo_list_for_the_showcase() {
        let input = serde_json::json!([
            {
                "name": "cnats",
                "description": "A NATS-backed chat client",
                "html_url": "https://project.uhhm.no/bl/cnats",
                "stargazers_count": 3,
                "private": false
            },
            {
                "name": "portal",
                "description": "This app",
                "html_url": "https://project.uhhm.no/uhhm/portal",
                "stargazers_count": 1,
                "private": false
            }
        ]);
        let filter = ".[] | {name: .name, description: .description, url: .html_url, stars: .stargazers_count}";

        let shaped = apply_jq(filter, &input).expect("filter runs");
        let items = shaped.as_array().expect("array output");
        assert_eq!(items.len(), 2);
        assert_eq!(items[0]["name"], "cnats");
        assert_eq!(items[0]["url"], "https://project.uhhm.no/bl/cnats");
        assert_eq!(items[0]["stars"], 3);
        // The filter never mentions `private` - confirms shaping
        // actually drops fields, not just passes the object through.
        assert!(items[0].get("private").is_none());
    }

    #[test]
    fn is_public_ip_rejects_loopback_and_private() {
        let loopback: std::net::IpAddr = "127.0.0.1".parse().unwrap();
        let private: std::net::IpAddr = "10.0.0.5".parse().unwrap();
        let link_local: std::net::IpAddr = "169.254.1.1".parse().unwrap();
        let public: std::net::IpAddr = "1.1.1.1".parse().unwrap();
        assert!(!is_public_ip(&loopback));
        assert!(!is_public_ip(&private));
        assert!(!is_public_ip(&link_local));
        assert!(is_public_ip(&public));
    }
}