package diskreadings

import (
	"encoding/json"
	"strings"
	"testing"
	"time"

	"git.novox.be/novox/mesh-sdk/go/catalogue"
)

// ADR 0571 clause 3: a reading keeps its seven-day peak and is written only when it changes; a partial size is no peak.
func TestAReadingKeepsItsPeakAndIsWrittenOnlyWhenItChanges(t *testing.T) {
	at := time.Date(2026, 10, 29, 12, 0, 0, 0, time.UTC)
	var prev *Reading
	for i, step := range []struct {
		day, size      int64
		partial, wrote bool
		peak           int64
	}{{20, 100, false, true, 100}, {20, 100, false, false, 100}, {21, 300, false, true, 300}, {22, 50, false, true, 300},
		{23, 9000, true, true, 300}, {29, 10, false, true, 50}, {30, 10, false, true, 10}} {
		now := time.Date(2026, 10, int(step.day), 1, 0, 0, 0, time.UTC)
		size := step.size
		m := Measured{SizeBytes: &size, MeasuredAt: &now, Precision: "exact"}
		if step.partial {
			m.Precision = "partial: stopped"
		}
		r, wrote := NextReading(prev, "ace", catalogue.PlacedDataItem{Module: "pg", ID: "data", Path: "/srv/pg"}, m, now)
		raw, _ := json.Marshal(r)
		back, err := DecodeReading(raw)
		if wrote != step.wrote || r.Peak == nil || *r.Peak != step.peak || err != nil || back.ID != "data" {
			t.Fatalf("reading %d: wrote %v, peak %v, read back %v", i, wrote, r.Peak, err)
		}
		prev = &r
	}
	// The first reading sets FirstSeen and every one after keeps it, as it keeps a retirement; an older reading reads as before.
	if first := time.Date(2026, 10, 20, 1, 0, 0, 0, time.UTC); !prev.FirstSeen.Equal(first) {
		t.Fatalf("first seen %s, not %s", prev.FirstSeen, first)
	}
	retired := *prev
	retired.RetiredAt, retired.RetiredWhy = at, "its module left ace"
	if r, _ := NextReading(&retired, "ace", retired.PlacedDataItem, retired.Measured, at.Add(time.Hour)); !r.RetiredAt.Equal(at) ||
		r.RetiredWhy != "its module left ace" || !r.FirstSeen.Equal(prev.FirstSeen) {
		t.Fatalf("a retired reading moved on as %+v", r)
	}
	if old, err := DecodeReading([]byte(`{"v":1,"node":"ace","module":"pg","item":"data"}`)); err != nil || !old.FirstSeen.IsZero() {
		t.Fatalf("a reading of before read as %+v: %v", old, err)
	}
	if raw, _ := json.Marshal(Reading{V: ReadingVersion}); strings.Contains(string(raw), "first_seen") || strings.Contains(string(raw), "retired") {
		t.Fatalf("zero fields were written: %s", raw)
	}
	if ReadingKey("ace", "pg", "data") != "ace.pg.data" || ReadingsBucket != "disk-load_readings" {
		t.Fatal("the readings' key or bucket moved")
	}
}