package notify

import (
	"flag"
	"os"
	"path/filepath"
	"sort"
	"testing"

	"gitea.dooplex.hu/admin/felhom-hub/internal/i18n"
	"time"
)

// Mail goldens — the measurement localisation slice 3 rests on (R-558).
//
// Every customer-facing mail the hub can send is rendered here and compared against bytes captured
// from the code as it stood BEFORE any string moved (felhom.eu 20aafc3dec20, hub v0.117.0). The
// claim "the Hungarian mails are unchanged" is then a diff, not a reading.
//
// THE RULE THAT MAKES THEM WORTH HAVING: a golden is never regenerated to make a change pass. It is
// regenerated only for a block that has been declared and measured, and the declaration says which
// mail and why. Slice 2 on the controller earned that sentence twice.
//
// Regenerate deliberately:  go test ./internal/notify/ -run TestCustomerMailGoldens -update-mail-goldens

var updateMailGoldens = flag.Bool("update-mail-goldens", false,
	"rewrite the captured mail goldens (deliberate, declared blocks only)")

// goldenClock is the instant every golden is stamped with. A fixed winter date, so the Budapest
// offset in the operator mail's `MST` field is stable too (CET, not CEST).
var goldenClock = time.Date(2026, 1, 15, 9, 30, 0, 0, time.UTC)

// mailCase is one rendered mail: a name for its golden file, and the call that produces it.
type mailCase struct {
	name    string
	render  func() (string, string) // subject, body
	comment string
}

// customerMailCases enumerates every customer mail the hub can produce.
//
// The event-type cases are generated FROM `customerMessages` itself rather than from a list retyped
// here, so a new entry cannot be added without a golden appearing beside it — the list cannot drift
// out of date the way a hand-maintained one does (R-423's lesson, other side).
func customerMailCases(lang string) []mailCase {
	var cases []mailCase

	keys := make([]string, 0, len(customerMessages))
	for k := range customerMessages {
		keys = append(keys, k)
	}
	sort.Strings(keys)

	// 1. Every known event type, rendered with no box message and no details — the plain shape.
	for _, k := range keys {
		k := k
		cases = append(cases, mailCase{
			name:   "customer_event_" + k,
			render: func() (string, string) { return FormatCustomerEmail(lang, "demo-fixture", k, "warning", "", "", "") },
		})
	}

	// 2. The shapes that are NOT one per event type: the fallbacks and the optional lines.
	cases = append(cases,
		mailCase{
			name:    "customer_shape_unknown_type_uses_box_message",
			comment: "an event type with no entry: the box's own Hungarian sentence IS the mail",
			render: func() (string, string) {
				return FormatCustomerEmail(lang, "demo-fixture", "disk_warning", "warning",
					"A /mnt/adat lemez 91%-ig megtelt (12,4 GB szabad).", "", "")
			},
		},
		mailCase{
			name:    "customer_shape_box_message_beside_entry",
			comment: "a known type AND a box message: the entry is the headline, the message is a line",
			render: func() (string, string) {
				return FormatCustomerEmail(lang, "demo-fixture", "backup_failed", "error",
					"A cel nincs beallitva.", "", "")
			},
		},
		mailCase{
			name:    "customer_shape_with_details",
			comment: "details render as the Megjegyzes line",
			render: func() (string, string) {
				return FormatCustomerEmail(lang, "demo-fixture", "app_deployed", "info", "", "", `{"app":"bentopdf"}`)
			},
		},
		mailCase{
			name:    "customer_shape_app_update_undone_names_the_app",
			comment: "v0.120.0: the entry names the app from details.stack_name; the box's sentence is the line",
			render: func() (string, string) {
				return FormatCustomerEmail(lang, "demo-fixture", "app_update_undone", "warning",
					"A(z) docmost frissitese nem sikerult.", "",
					`{"app":"docmost","stack_name":"docmost","from":{"docmost":"docmost:0.95.0"},"to":{"docmost":"docmost:0.96.0"}}`)
			},
		},
		mailCase{
			name:    "customer_shape_app_update_held_names_the_app",
			comment: "v0.120.0: the held entry names the app; the hold sentence is the line",
			render: func() (string, string) {
				return FormatCustomerEmail(lang, "demo-fixture", "app_update_held", "error",
					"A frissites nem sikerult, es az automatikus visszaallitas sem.", "",
					`{"app":"vikunja","stack_name":"vikunja","copy_tier":2}`)
			},
		},
		mailCase{
			name:    "customer_shape_empty_details_object_is_omitted",
			comment: "{} is not details",
			render: func() (string, string) {
				return FormatCustomerEmail(lang, "demo-fixture", "app_deployed", "info", "", "", "{}")
			},
		},
		mailCase{
			name:    "customer_shape_unknown_severity_prints_raw",
			comment: "an unlabelled severity falls through to its own name",
			render: func() (string, string) {
				return FormatCustomerEmail(lang, "demo-fixture", "test", "verbose", "", "", "")
			},
		},
	)
	for _, sev := range []string{"info", "warning", "error", "critical"} {
		sev := sev
		cases = append(cases, mailCase{
			name:   "customer_severity_" + sev,
			render: func() (string, string) { return FormatCustomerEmail(lang, "demo-fixture", "test", sev, "", "", "") },
		})
	}

	// 3. The claim arc and the self-bind link — the mails sent before any box reports.
	for _, kind := range []string{"claim", "reset", "reenroll", "claimed"} {
		kind := kind
		cases = append(cases, mailCase{
			name: "claim_" + kind,
			render: func() (string, string) {
				return FormatClaimEmail(lang, kind, "demo-fixture", "fixture.example", "alma-korte-szilva")
			},
		})
	}
	cases = append(cases, mailCase{
		name: "selfbind",
		render: func() (string, string) {
			return FormatSelfBindEmail(lang, "demo-fixture", "https://hub.felhom.eu/bind/FIXTURETOKEN")
		},
	})

	// 4. The OPERATOR mails. They are English and this slice does not touch them — which is exactly
	//    why they are goldened: the claim "the operator's mail did not move" needs the same diff.
	cases = append(cases,
		mailCase{
			name: "operator_event_backup_failed",
			render: func() (string, string) {
				return FormatOperatorEmail("demo-fixture", "backup_failed", "error", "A mentes sikertelen.", "")
			},
		},
		mailCase{
			name:   "operator_event_recovered",
			render: func() (string, string) { return FormatOperatorEmail("demo-fixture", "node_recovered", "info", "", "") },
		},
		mailCase{
			name:    "operator_backup_run_failures_digest",
			comment: "the R-182 digest — operator-only, already English, never localised",
			render: func() (string, string) {
				return FormatOperatorEmail("demo-fixture", "backup_run_failures", "error", "3 app failed", `{
					"run_id":"r1","run_kind":"nightly","failed":2,"attempted":4,
					"target_path":"/mnt/backup","used_gb":81.5,"avail_gb":12.5,"total_gb":94.0,
					"used_percent":86.7,"space_known":true,
					"apps":[{"app":"bookstack","leg":"db","reason":"mysqldump exit 1 — /mnt/backup: 81.5/94.0 GB used (87%), 12.5 GB free"},
					        {"app":"vaultwarden","leg":"volumes","reason":"no space left on device"}]}`)
			},
		},
	)
	return cases
}

func goldenDir(lang string) string { return filepath.Join("testdata", "mail_goldens", lang) }

// renderGolden is the on-disk form: subject and body in one file, so a diff shows both.
func renderGolden(c mailCase) string {
	subject, body := c.render()
	out := ""
	if c.comment != "" {
		out += "# " + c.comment + "\n"
	}
	return out + "SUBJECT: " + subject + "\n---\n" + body + "\n"
}

func TestCustomerMailGoldens(t *testing.T) {
	old := nowFn
	nowFn = func() time.Time { return goldenClock }
	t.Cleanup(func() { nowFn = old })

	for _, lang := range i18n.Supported {
		t.Run(lang, func(t *testing.T) { runMailGoldens(t, lang) })
	}
}

// runMailGoldens renders every mail in one language and diffs it against that language's captured
// bytes. Hungarian proves nothing moved; English proves what shipped is what was reviewed.
func runMailGoldens(t *testing.T, lang string) {
	cases := customerMailCases(lang)
	if len(cases) < 50 {
		t.Fatalf("only %d mail cases enumerated — the table stopped covering the mails", len(cases))
	}

	if *updateMailGoldens {
		if err := os.MkdirAll(goldenDir(lang), 0o755); err != nil {
			t.Fatal(err)
		}
		for _, c := range cases {
			p := filepath.Join(goldenDir(lang), c.name+".txt")
			if err := os.WriteFile(p, []byte(renderGolden(c)), 0o644); err != nil {
				t.Fatal(err)
			}
		}
		t.Logf("wrote %d %s mail goldens to %s", len(cases), lang, goldenDir(lang))
		return
	}

	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			p := filepath.Join(goldenDir(lang), c.name+".txt")
			want, err := os.ReadFile(p)
			if err != nil {
				t.Fatalf("no golden for %s — capture it deliberately: %v", c.name, err)
			}
			got := renderGolden(c)
			if got != string(want) {
				t.Errorf("mail %s changed.\n--- golden ---\n%s\n--- now ---\n%s", c.name, want, got)
			}
		})
	}

	// Every golden on disk belongs to a case: a file left behind after a mail is deleted would
	// otherwise sit there proving nothing about a mail that no longer exists.
	entries, err := os.ReadDir(goldenDir(lang))
	if err != nil {
		t.Fatal(err)
	}
	known := map[string]bool{}
	for _, c := range cases {
		known[c.name+".txt"] = true
	}
	for _, e := range entries {
		if !known[e.Name()] {
			t.Errorf("orphan golden %s — no case renders it", e.Name())
		}
	}
}