package api

import (
	"net/http"

	"github.com/gin-gonic/gin"
)

// responseControllerKey is where captureController stashes the controller in
// the gin context for responseController to find.
const responseControllerKey = "pansy.responseController"

// captureController hands every handler an http.ResponseController that can
// actually reach the connection. It MUST be the first middleware on the engine.
//
// A ResponseController finds the connection's deadline setters by unwrapping
// the ResponseWriter it was built from, one layer at a time, until it reaches
// one that has them. gin's own writer unwraps cleanly. The logging middleware's
// does not: it replaces c.Writer with a type that embeds the gin.ResponseWriter
// INTERFACE, which has no Unwrap, so a controller built from c.Writer inside a
// handler stops there and every SetReadDeadline/SetWriteDeadline returns
// ErrNotSupported. That left the per-frame SSE deadline (#78) and the scan
// upload's extensions dead in production while their tests — on a bare engine
// with no logging — passed: long agent turns were cut at the server's absolute
// 30s WriteTimeout, and the client saw "The connection dropped partway through."
//
// Building the controller here, ahead of every wrapper, sidesteps the question
// of what any later middleware does to the writer. Handlers that extend a
// deadline take it from responseController; sse_deadline_test.go runs the
// scenario through New so a reorder or a new wrapper fails a test.
func captureController() gin.HandlerFunc {
	return func(c *gin.Context) {
		c.Set(responseControllerKey, http.NewResponseController(c.Writer))
		c.Next()
	}
}

// responseController returns the controller captureController stored, or — on
// an engine without that middleware, which only tests build — one made from
// c.Writer as it stands.
func responseController(c *gin.Context) *http.ResponseController {
	if v, ok := c.Get(responseControllerKey); ok {
		if rc, ok := v.(*http.ResponseController); ok {
			return rc
		}
	}
	return http.NewResponseController(c.Writer)
}