package middleware

import (
	"github.com/labstack/echo/v4"
)

type (
	// RequestIDConfig defines the config for RequestID middleware.
	RequestIDConfig struct {
		// Skipper defines a function to skip middleware.
		Skipper Skipper

		// Generator defines a function to generate an ID.
		// Optional. Defaults to generator for random string of length 32.
		Generator func() string

		// RequestIDHandler defines a function which is executed for a request id.
		RequestIDHandler func(echo.Context, string)

		// TargetHeader defines what header to look for to populate the id
		TargetHeader string
	}
)

var (
	// DefaultRequestIDConfig is the default RequestID middleware config.
	DefaultRequestIDConfig = RequestIDConfig{
		Skipper:      DefaultSkipper,
		Generator:    generator,
		TargetHeader: echo.HeaderXRequestID,
	}
)

// RequestID returns a X-Request-ID middleware.
func RequestID() echo.MiddlewareFunc {
	return RequestIDWithConfig(DefaultRequestIDConfig)
}

// RequestIDWithConfig returns a X-Request-ID middleware with config.
func RequestIDWithConfig(config RequestIDConfig) echo.MiddlewareFunc {
	// Defaults
	if config.Skipper == nil {
		config.Skipper = DefaultRequestIDConfig.Skipper
	}
	if config.Generator == nil {
		config.Generator = generator
	}
	if config.TargetHeader == "" {
		config.TargetHeader = echo.HeaderXRequestID
	}

	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c echo.Context) error {
			if config.Skipper(c) {
				return next(c)
			}

			req := c.Request()
			res := c.Response()
			rid := req.Header.Get(config.TargetHeader)
			if rid == "" {
				rid = config.Generator()
			}
			res.Header().Set(config.TargetHeader, rid)
			if config.RequestIDHandler != nil {
				config.RequestIDHandler(c, rid)
			}

			return next(c)
		}
	}
}

func generator() string {
	return randomString(32)
}