// Package echo provides the conformance fixture adapters.
//
// Two revisions over the same data: R-1 exposes only a collection, R-2 adds the
// convenience resource. Both are ordinary deterministic HTTP handlers, which is
// the point — an adapter is a normal service, and fluid-core sits in front of
// it without asking anything of it.
package echo

import (
	"encoding/json"
	"net/http"
	"sort"
	"time"
)

// Entry is one record the fixture serves.
type Entry struct {
	ID        string    `json:"id"`
	Title     string    `json:"title"`
	CreatedAt time.Time `json:"created_at"`
}

// Data returns a deterministic set of entries.
//
// Fixed timestamps rather than time.Now: a conformance suite whose fixture
// changes between runs cannot distinguish a regression from the clock.
func Data() []Entry {
	base := time.Date(2026, 9, 1, 12, 0, 0, 0, time.UTC)
	return []Entry{
		{ID: "e-1", Title: "the river reached the forge", CreatedAt: base},
		{ID: "e-2", Title: "nine doors stayed honest", CreatedAt: base.Add(24 * time.Hour)},
		{ID: "e-3", Title: "the reviewing side", CreatedAt: base.Add(48 * time.Hour)},
	}
}

// NewR1 returns the collection-only adapter.
//
// A consumer wanting the newest entry must fetch the whole collection, sort it
// and discard the rest. That is the interface pressure the fixture generates.
func NewR1() http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("/v1/entries", func(w http.ResponseWriter, r *http.Request) {
		writeJSON(w, Data())
	})
	return mux
}

// NewR2 returns the adapter with the convenience resource added.
func NewR2() http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("/v1/entries", func(w http.ResponseWriter, r *http.Request) {
		writeJSON(w, Data())
	})
	mux.HandleFunc("/v1/entries/latest", func(w http.ResponseWriter, r *http.Request) {
		entries := Data()
		sort.Slice(entries, func(i, j int) bool {
			return entries[i].CreatedAt.After(entries[j].CreatedAt)
		})
		writeJSON(w, entries[0])
	})
	return mux
}

func writeJSON(w http.ResponseWriter, v any) {
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(v)
}