github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822: negotiate HTTP Accept header content type using goautoneg

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: negotiate HTTP Accept header content type using goautoneg
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/munnerz/goautoneg@v0.0.0-20191010083416-a7dc8b61c822
Demonstrate these symbols/APIs:
  - Negotiate
  - ParseAccept

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:cb77f3449f65beed108e56c17674e85655f85fe81ce457057062e98f63d1adf5","contract":["Negotiate selects the highest quality media type among available alternatives","Negotiate resolves wildcards and subtype wildcards according to quality values","Negotiate returns an empty string when no alternatives match the accept header","ParseAccept parses media types, quality values, and parameters into ordered clauses","ParseAccept parses wildcard media types with quality parameters"],"goal":"negotiate HTTP Accept header content type using goautoneg","kind":"HOW","packages":["pkg:golang/github.com/munnerz/goautoneg@v0.0.0-20191010083416-a7dc8b61c822"],"schemaVersion":1,"symbols":["Negotiate","ParseAccept"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/munnerz/goautoneg@v0.0.0-20191010083416-a7dc8b61c822"],"schemaVersion":1,"subject":"pkg:golang/github.com/munnerz/goautoneg@v0.0.0-20191010083416-a7dc8b61c822","symbols":["Negotiate","ParseAccept"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect

github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=

package main

import (
	"fmt"

	"github.com/munnerz/goautoneg"
)

func main() {
	header := "text/html, application/xhtml+xml, application/xml;q=0.9, */*;q=0.8"
	alternatives := []string{"application/json", "text/html", "application/xml"}

	selected := goautoneg.Negotiate(header, alternatives)
	fmt.Printf("Negotiated content type: %s\n", selected)

	clauses := goautoneg.ParseAccept(header)
	fmt.Printf("Parsed %d clauses\n", len(clauses))
}

{
  "schemaVersion": 1,
  "goal": "negotiate HTTP Accept header content type using goautoneg",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/munnerz/goautoneg@v0.0.0-20191010083416-a7dc8b61c822"
  ],
  "symbols": [
    "Negotiate",
    "ParseAccept"
  ]
}

package main

import (
	"fmt"
	"math"
	"os"

	"github.com/munnerz/goautoneg"
)

func main() {
	if err := runContract(); err != nil {
		fmt.Fprintf(os.Stderr, "Contract verification failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("All goautoneg contract assertions passed successfully.")
}

func runContract() error {
	// Assertion 1: Negotiate selects the highest quality media type among available alternatives
	header1 := "text/plain;q=0.5, application/json;q=0.9, text/html;q=0.8"
	alts1 := []string{"text/plain", "application/json", "text/html"}
	if got := goautoneg.Negotiate(header1, alts1); got != "application/json" {
		return fmt.Errorf("assertion 1 failed: expected %q, got %q", "application/json", got)
	}

	// Assertion 2: Negotiate resolves wildcards and subtype wildcards according to quality values
	header2 := "image/*;q=0.8, text/*;q=0.6, */*;q=0.1"
	alts2 := []string{"application/pdf", "image/png", "text/plain"}
	if got := goautoneg.Negotiate(header2, alts2); got != "image/png" {
		return fmt.Errorf("assertion 2 failed: expected %q, got %q", "image/png", got)
	}

	// Assertion 3: Negotiate returns an empty string when no alternatives match the accept header
	header3 := "application/json, application/xml"
	alts3 := []string{"image/png", "text/html"}
	if got := goautoneg.Negotiate(header3, alts3); got != "" {
		return fmt.Errorf("assertion 3 failed: expected empty string, got %q", got)
	}

	// Assertion 4: ParseAccept parses media types, quality values, and parameters into ordered clauses
	header4 := "text/html;level=1;q=0.7, application/json;q=1.0, text/plain;q=0.5"
	clauses := goautoneg.ParseAccept(header4)
	if len(clauses) != 3 {
		return fmt.Errorf("assertion 4 failed: expected 3 clauses, got %d", len(clauses))
	}
	if clauses[0].Type != "application" || clauses[0].SubType != "json" || math.Abs(clauses[0].Q-1.0) > 1e-4 {
		return fmt.Errorf("assertion 4 failed: clause 0 mismatch: %+v", clauses[0])
	}
	if clauses[1].Type != "text" || clauses[1].SubType != "html" || math.Abs(clauses[1].Q-0.7) > 1e-4 || clauses[1].Params["level"] != "1" {
		return fmt.Errorf("assertion 4 failed: clause 1 mismatch: %+v", clauses[1])
	}
	if clauses[2].Type != "text" || clauses[2].SubType != "plain" || math.Abs(clauses[2].Q-0.5) > 1e-4 {
		return fmt.Errorf("assertion 4 failed: clause 2 mismatch: %+v", clauses[2])
	}

	// Assertion 5: ParseAccept parses wildcard media types with quality parameters
	header5 := "*/*;q=0.2"
	clauses5 := goautoneg.ParseAccept(header5)
	if len(clauses5) != 1 {
		return fmt.Errorf("assertion 5 failed: expected 1 clause, got %d", len(clauses5))
	}
	if clauses5[0].Type != "*" || clauses5[0].SubType != "*" || math.Abs(clauses5[0].Q-0.2) > 1e-4 {
		return fmt.Errorf("assertion 5 failed: clause mismatch: %+v", clauses5[0])
	}

	return nil
}