//! Reading response bodies back out, by response id.
//!
//! Plugins only ever name a response. Where its bytes actually live — files the
//! engine wrote under `<data dir>/responses/<id>` today, blob rows later — is
//! behind [`ResponseBodyStore`], so moving the bytes is a change to this file
//! and nothing a plugin can see.
//!
//! Only saved responses are reachable by id. A send that saved nothing hands
//! its body back with the reply instead, which is the only copy of it there is.

use crate::error::Result;
use std::fs::File;
use std::io::{Read, Seek, SeekFrom};
use yaak_models::models::HttpResponseState;
use yaak_models::query_manager::QueryManager;

/// The most bytes one read will hand back, however much was asked for.
///
/// A chunk is buffered whole and, on the desktop transport, base64'd into a
/// single WebSocket frame, so an unbounded request is a way to make the host
/// allocate on a plugin's say-so.
pub const MAX_CHUNK_BYTES: u64 = 8 * 1024 * 1024;

/// What a stored body is, without reading any of it.
#[derive(Debug, Clone, Default)]
pub struct ResponseBodyInfo {
    /// Bytes actually stored, which is not necessarily what `Content-Length`
    /// claimed. Zero when the response has no body.
    pub content_length: u64,
    /// The response's `Content-Type` header, verbatim.
    pub content_type: Option<String>,
    /// Whether the response has finished arriving, so `content_length` is
    /// final. A body still being written grows past it.
    pub complete: bool,
}

/// Somewhere response bodies can be read from, a window at a time.
///
/// Reads are repeatable — the bytes are durable, so nothing is consumed by
/// looking at it.
pub trait ResponseBodyStore {
    fn info(&self, response_id: &str) -> Result<ResponseBodyInfo>;

    /// Bytes `[offset, offset + length)`, clamped to what is there. A short
    /// read means the body ended.
    fn read_chunk(&self, response_id: &str, offset: u64, length: u64) -> Result<Vec<u8>>;
}

/// The desktop and CLI store: the database says where the file is, and the
/// filesystem holds it.
pub struct FileResponseBodyStore<'a> {
    query_manager: &'a QueryManager,
}

impl<'a> FileResponseBodyStore<'a> {
    pub fn new(query_manager: &'a QueryManager) -> Self {
        Self { query_manager }
    }

    /// The file backing a response, or `None` when it stored no body.
    ///
    /// Only responses the store knows about are reachable here. A send with no
    /// request behind it never reaches the store at all, and its bytes come
    /// back from the send instead — see `SendHttpRequestResponse::body`.
    fn body_path(&self, response_id: &str) -> Result<Option<String>> {
        Ok(self.query_manager.connect().get_http_response(response_id)?.body_path)
    }
}

impl ResponseBodyStore for FileResponseBodyStore<'_> {
    fn info(&self, response_id: &str) -> Result<ResponseBodyInfo> {
        let response = self.query_manager.connect().get_http_response(response_id)?;

        let content_type = response
            .headers
            .iter()
            .find(|h| h.name.eq_ignore_ascii_case("content-type"))
            .map(|h| h.value.clone());

        let content_length = match response.body_path {
            Some(path) => std::fs::metadata(path)?.len(),
            None => 0,
        };

        Ok(ResponseBodyInfo {
            content_length,
            content_type,
            // Closed is the one terminal state: success, error, and cancel all end there.
            complete: matches!(response.state, HttpResponseState::Closed),
        })
    }

    fn read_chunk(&self, response_id: &str, offset: u64, length: u64) -> Result<Vec<u8>> {
        let Some(path) = self.body_path(response_id)? else {
            return Ok(Vec::new());
        };

        let length = length.min(MAX_CHUNK_BYTES);
        if length == 0 {
            return Ok(Vec::new());
        }

        let mut file = File::open(path)?;
        file.seek(SeekFrom::Start(offset))?;

        let mut buf = Vec::new();
        file.take(length).read_to_end(&mut buf)?;
        Ok(buf)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::io::Write;
    use tempfile::TempDir;
    use yaak_models::models::{HttpRequest, HttpResponse, HttpResponseHeader, Workspace};
    use yaak_models::util::UpdateSource;

    fn seed(body: Option<&[u8]>) -> (QueryManager, TempDir, String) {
        let temp_dir = TempDir::new().unwrap();
        let (query_manager, blob_manager, _rx) = yaak_models::init_standalone(
            &temp_dir.path().join("db.sqlite"),
            &temp_dir.path().join("blobs.sqlite"),
        )
        .unwrap();

        query_manager
            .connect()
            .upsert_workspace(
                &Workspace { id: "wk_test".to_string(), ..Default::default() },
                &UpdateSource::Sync,
            )
            .unwrap();

        query_manager
            .connect()
            .upsert_http_request(
                &HttpRequest {
                    id: "rq_test".to_string(),
                    workspace_id: "wk_test".to_string(),
                    ..Default::default()
                },
                &UpdateSource::Sync,
            )
            .unwrap();

        let body_path = body.map(|bytes| {
            let path = temp_dir.path().join("body");
            let mut f = std::fs::File::create(&path).unwrap();
            f.write_all(bytes).unwrap();
            path.to_string_lossy().to_string()
        });

        let response = query_manager
            .connect()
            .upsert_http_response(
                &HttpResponse {
                    workspace_id: "wk_test".to_string(),
                    request_id: "rq_test".to_string(),
                    body_path,
                    headers: vec![HttpResponseHeader {
                        name: "Content-Type".to_string(),
                        value: "application/json; charset=utf-8".to_string(),
                    }],
                    ..Default::default()
                },
                &UpdateSource::Sync,
                &blob_manager,
            )
            .unwrap();

        let id = response.id.clone();
        (query_manager, temp_dir, id)
    }

    #[test]
    fn info_reports_stored_size_and_content_type() {
        let (qm, _tmp, id) = seed(Some(b"hello world"));
        let info = FileResponseBodyStore::new(&qm).info(&id).unwrap();
        assert_eq!(info.content_length, 11);
        assert_eq!(info.content_type.as_deref(), Some("application/json; charset=utf-8"));
    }

    #[test]
    fn chunks_cover_the_body_and_stop_short_at_the_end() {
        let (qm, _tmp, id) = seed(Some(b"hello world"));
        let store = FileResponseBodyStore::new(&qm);
        assert_eq!(store.read_chunk(&id, 0, 5).unwrap(), b"hello");
        assert_eq!(store.read_chunk(&id, 6, 100).unwrap(), b"world");
        assert!(store.read_chunk(&id, 11, 100).unwrap().is_empty());
        // Reading the same window twice gives the same bytes; nothing is consumed.
        assert_eq!(store.read_chunk(&id, 0, 5).unwrap(), b"hello");
    }

    #[test]
    fn a_response_with_no_body_is_empty_not_an_error() {
        let (qm, _tmp, id) = seed(None);
        let store = FileResponseBodyStore::new(&qm);
        assert_eq!(store.info(&id).unwrap().content_length, 0);
        assert!(store.read_chunk(&id, 0, 100).unwrap().is_empty());
    }

    #[test]
    fn complete_tracks_whether_the_response_has_closed() {
        let (qm, _tmp, id) = seed(Some(b"partial"));
        // Seeded responses default to Initialized: still arriving.
        assert!(!FileResponseBodyStore::new(&qm).info(&id).unwrap().complete);

        let mut response = qm.connect().get_http_response(&id).unwrap();
        response.state = HttpResponseState::Closed;
        qm.connect().update_http_response_if_id(&response, &UpdateSource::Sync).unwrap();

        assert!(FileResponseBodyStore::new(&qm).info(&id).unwrap().complete);
    }

    #[test]
    fn an_unknown_response_fails() {
        let (qm, _tmp, _id) = seed(Some(b"hi"));
        assert!(FileResponseBodyStore::new(&qm).info("rs_nope").is_err());
    }

    #[test]
    fn an_unsaved_response_is_not_reachable_by_id() {
        // Its bytes rode back with the send; there is nothing here to find, and
        // guessing at a file named for the id is exactly what this must not do.
        let (qm, tmp, _id) = seed(Some(b"hi"));
        std::fs::write(tmp.path().join("rs_ephemeral1"), b"access_token=abc").unwrap();

        assert!(FileResponseBodyStore::new(&qm).info("rs_ephemeral1").is_err());
    }
}