use http_body_util::{BodyExt, Full};
use hyper::StatusCode;
use hyper::body::{Bytes, Incoming};
use serde::Serialize;
use serde::de::DeserializeOwned;

use super::model::{ApiFailure, ErrorBody, ErrorResponse, SuccessResponse};

pub(super) fn success_response<T: Serialize>(
    status: StatusCode,
    data: T,
    revision: String,
) -> hyper::Response<Full<Bytes>> {
    let payload = SuccessResponse {
        ok: true,
        data,
        revision,
    };
    let body = serde_json::to_vec(&payload).unwrap_or_else(|_| b"{\"ok\":false}".to_vec());
    hyper::Response::builder()
        .status(status)
        .header("content-type", "application/json; charset=utf-8")
        .body(Full::new(Bytes::from(body)))
        .unwrap()
}

pub(super) fn error_response(request_id: u64, failure: ApiFailure) -> hyper::Response<Full<Bytes>> {
    let payload = ErrorResponse {
        ok: false,
        error: ErrorBody {
            code: failure.code,
            message: failure.message,
        },
        request_id,
    };
    let body = serde_json::to_vec(&payload).unwrap_or_else(|_| {
        format!(
            "{{\"ok\":false,\"error\":{{\"code\":\"internal_error\",\"message\":\"serialization failed\"}},\"request_id\":{}}}",
            request_id
        )
        .into_bytes()
    });
    hyper::Response::builder()
        .status(failure.status)
        .header("content-type", "application/json; charset=utf-8")
        .body(Full::new(Bytes::from(body)))
        .unwrap()
}

pub(super) async fn read_json<T: DeserializeOwned>(
    body: Incoming,
    limit: usize,
) -> Result<T, ApiFailure> {
    let bytes = read_body_with_limit(body, limit).await?;
    serde_json::from_slice(&bytes).map_err(|_| ApiFailure::bad_request("Invalid JSON body"))
}

pub(super) async fn read_optional_json<T: DeserializeOwned>(
    body: Incoming,
    limit: usize,
) -> Result<Option<T>, ApiFailure> {
    let bytes = read_body_with_limit(body, limit).await?;
    if bytes.is_empty() {
        return Ok(None);
    }
    serde_json::from_slice(&bytes)
        .map(Some)
        .map_err(|_| ApiFailure::bad_request("Invalid JSON body"))
}

async fn read_body_with_limit(body: Incoming, limit: usize) -> Result<Vec<u8>, ApiFailure> {
    let mut collected = Vec::new();
    let mut body = body;
    while let Some(frame_result) = body.frame().await {
        let frame = frame_result.map_err(|_| ApiFailure::bad_request("Invalid request body"))?;
        if let Some(chunk) = frame.data_ref() {
            if collected.len().saturating_add(chunk.len()) > limit {
                return Err(ApiFailure::new(
                    StatusCode::PAYLOAD_TOO_LARGE,
                    "payload_too_large",
                    format!("Body exceeds {} bytes", limit),
                ));
            }
            collected.extend_from_slice(chunk);
        }
    }
    Ok(collected)
}