package middleware

import (
	"github.com/labstack/echo/v5"
)

// ScriptHashThemeFlashGuard is the CSP script-src hash of the theme flash
// guard's inline script (the app's only inline script). Enforced against
// the rendered component by security_headers_test.go.
const ScriptHashThemeFlashGuard = "'sha256-JYIVpFyKdLUtWizMha0v69f6yHds+GbJRBWjvpuECBY='"

// SecurityHeadersMiddleware adds security headers to all responses
func SecurityHeadersMiddleware() echo.MiddlewareFunc {
	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c *echo.Context) error {
			// Add security headers
			c.Response().Header().Set("X-Content-Type-Options", "nosniff")
			c.Response().Header().Set("X-Frame-Options", "DENY")
			c.Response().Header().Set("X-XSS-Protection", "1; mode=block")
			c.Response().Header().Set("Strict-Transport-Security", "max-age=31536000; includeSubDomains; preload")
			// script-src notes: 'unsafe-inline' is required by the pre-paint
			// CSP-safe Alpine build (@alpinejs/csp) needs no eval — do NOT
			// add 'unsafe-eval' here without removing that build.
			//
			// The inline script allow-list: the theme flash guard is the
			// ONLY inline script in the app, and its byte-stable content is
			// hashed into script-src (sha256 of the bytes between
			// <script> and </script> as rendered by
			// templates.ThemeFlashGuard()). Editing the guard requires
			// recomputing the hash — enforced by
			// internal/middleware/security_headers_test.go, which renders
			// the component and asserts the hash matches.
			//
			// style-src keeps 'unsafe-inline' for htmx-injected styles and
			// Alpine :style attribute writes.
			// font/img blob: — the reader renders EPUB-embedded fonts and
			// images from blob: URLs inside the foliate content frame.
			c.Response().Header().Set("Content-Security-Policy", "default-src 'self'; script-src 'self' "+ScriptHashThemeFlashGuard+"; style-src 'self' 'unsafe-inline'; img-src 'self' data: https: blob:; font-src 'self' data: blob:; frame-src 'self' blob:")
			c.Response().Header().Set("Referrer-Policy", "strict-origin-when-cross-origin")
			c.Response().Header().Set("Permissions-Policy", "geolocation=(), microphone=(), camera=()")

			return next(c)
		}
	}
}