package api

import (
	"strings"
	"testing"
	"time"
)

// A realistic feed: UTC stamps, a TZID-qualified local time, an all-day event,
// folded lines, escaped text, and CRLF endings — all of which appear in the
// sports-schedule feeds this was written for.
const sampleICS = "BEGIN:VCALENDAR\r\n" +
	"VERSION:2.0\r\n" +
	"PRODID:-//Test//EN\r\n" +
	"BEGIN:VEVENT\r\n" +
	"UID:game-1@example.com\r\n" +
	"DTSTART:20260913T201500Z\r\n" +
	"DTEND:20260913T231500Z\r\n" +
	"SUMMARY:Seahawks at 49ers\r\n" +
	"LOCATION:Levi's Stadium\r\n" +
	"END:VEVENT\r\n" +
	"BEGIN:VEVENT\r\n" +
	"UID:game-2@example.com\r\n" +
	"DTSTART;TZID=America/Los_Angeles:20260920T131500\r\n" +
	"DTEND;TZID=America/Los_Angeles:20260920T161500\r\n" +
	"SUMMARY:Seahawks vs. Saints\r\n" +
	"DESCRIPTION:Home opener\\, kickoff 1:15pm\\nGates open at 11am\r\n" +
	"END:VEVENT\r\n" +
	"BEGIN:VEVENT\r\n" +
	"UID:bye-week@example.com\r\n" +
	"DTSTART;VALUE=DATE:20261012\r\n" +
	"DTEND;VALUE=DATE:20261013\r\n" +
	"SUMMARY:Bye week\r\n" +
	"END:VEVENT\r\n" +
	"BEGIN:VEVENT\r\n" +
	"UID:folded@example.com\r\n" +
	"DTSTART:20261019T170000Z\r\n" +
	"DTEND:20261019T200000Z\r\n" +
	// Folded mid-word on purpose: unfolding removes the CRLF and exactly one
	// leading space, so "...that the fe" + " " + "ed has..." must rejoin as
	// "that the feed has...". Folding at a word boundary would not distinguish
	// a correct implementation from one that also eats a real space.
	"SUMMARY:A very long game title that the fe\r\n" +
	" ed has folded across two lines\r\n" +
	"END:VEVENT\r\n" +
	"END:VCALENDAR\r\n"

func parseOrFail(t *testing.T, body string) []ICSEvent {
	t.Helper()
	events, err := ParseICS(strings.NewReader(body))
	if err != nil {
		t.Fatalf("ParseICS: %v", err)
	}
	return events
}

func TestParseICS_ReadsAllEvents(t *testing.T) {
	events := parseOrFail(t, sampleICS)
	if len(events) != 4 {
		t.Fatalf("got %d events, want 4: %+v", len(events), events)
	}
}

func TestParseICS_UTCTimestamps(t *testing.T) {
	e := parseOrFail(t, sampleICS)[0]
	if e.UID != "game-1@example.com" {
		t.Errorf("UID = %q", e.UID)
	}
	if e.Summary != "Seahawks at 49ers" {
		t.Errorf("Summary = %q", e.Summary)
	}
	want := time.Date(2026, 9, 13, 20, 15, 0, 0, time.UTC)
	if !e.Start.Equal(want) {
		t.Errorf("Start = %v, want %v", e.Start.UTC(), want)
	}
	if !e.End.Equal(time.Date(2026, 9, 13, 23, 15, 0, 0, time.UTC)) {
		t.Errorf("End = %v", e.End.UTC())
	}
	if e.AllDay {
		t.Error("a timed event was marked all-day")
	}
}

// A TZID-qualified time is a wall-clock time in that zone, not UTC. Reading it
// as UTC would put a 1:15pm Pacific kickoff on the timeline at 1:15pm local —
// silently, and only wrong by the offset.
func TestParseICS_TZIDIsInterpretedInThatZone(t *testing.T) {
	e := parseOrFail(t, sampleICS)[1]
	la, err := time.LoadLocation("America/Los_Angeles")
	if err != nil {
		t.Skipf("tzdata unavailable: %v", err)
	}
	want := time.Date(2026, 9, 20, 13, 15, 0, 0, la)
	if !e.Start.Equal(want) {
		t.Errorf("Start = %v (%v), want %v", e.Start, e.Start.UTC(), want.UTC())
	}
}

func TestParseICS_AllDayEvent(t *testing.T) {
	e := parseOrFail(t, sampleICS)[2]
	if !e.AllDay {
		t.Error("VALUE=DATE event should be all-day")
	}
	if e.Start.Year() != 2026 || e.Start.Month() != time.October || e.Start.Day() != 12 {
		t.Errorf("Start = %v, want 2026-10-12", e.Start)
	}
}

// Folded lines: a leading space or tab continues the previous line. Not
// unfolding leaves the title truncated at the fold.
func TestParseICS_UnfoldsLines(t *testing.T) {
	e := parseOrFail(t, sampleICS)[3]
	want := "A very long game title that the feed has folded across two lines"
	if e.Summary != want {
		t.Errorf("Summary = %q, want %q", e.Summary, want)
	}
}

// Text values escape commas, semicolons, backslashes and newlines.
func TestParseICS_UnescapesText(t *testing.T) {
	e := parseOrFail(t, sampleICS)[1]
	want := "Home opener, kickoff 1:15pm\nGates open at 11am"
	if e.Description != want {
		t.Errorf("Description = %q, want %q", e.Description, want)
	}
}

func TestParseICS_LocationIsCaptured(t *testing.T) {
	if got := parseOrFail(t, sampleICS)[0].Location; got != "Levi's Stadium" {
		t.Errorf("Location = %q", got)
	}
}

// An event with no DTEND gets a sensible end rather than a zero time, which
// would render as a 56-year-long event.
func TestParseICS_MissingDTENDDefaults(t *testing.T) {
	body := "BEGIN:VCALENDAR\r\nBEGIN:VEVENT\r\nUID:x\r\nDTSTART:20260913T201500Z\r\nSUMMARY:No end\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n"
	e := parseOrFail(t, body)[0]
	if !e.End.After(e.Start) {
		t.Errorf("End %v should be after Start %v", e.End, e.Start)
	}
}

// Events with no usable start are skipped rather than landing at the zero time,
// where they would sort to the top of the timeline forever.
func TestParseICS_SkipsEventsWithoutAStart(t *testing.T) {
	body := "BEGIN:VCALENDAR\r\nBEGIN:VEVENT\r\nUID:x\r\nSUMMARY:No start\r\nEND:VEVENT\r\n" +
		"BEGIN:VEVENT\r\nUID:y\r\nDTSTART:20260913T201500Z\r\nSUMMARY:Fine\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n"
	events := parseOrFail(t, body)
	if len(events) != 1 || events[0].Summary != "Fine" {
		t.Errorf("got %+v, want only the event with a start", events)
	}
}

func TestParseICS_HandlesLFOnlyLineEndings(t *testing.T) {
	body := strings.ReplaceAll(sampleICS, "\r\n", "\n")
	if got := len(parseOrFail(t, body)); got != 4 {
		t.Errorf("got %d events with LF endings, want 4", got)
	}
}

// Anything that is not a calendar must be a clear error, not silently zero
// events — an HTML error page from a dead feed URL is the common case.
func TestParseICS_RejectsNonCalendarContent(t *testing.T) {
	if _, err := ParseICS(strings.NewReader("<html><body>404 Not Found</body></html>")); err == nil {
		t.Error("expected an error for non-calendar content")
	}
}

func TestParseICS_EmptyCalendarIsNotAnError(t *testing.T) {
	events, err := ParseICS(strings.NewReader("BEGIN:VCALENDAR\r\nVERSION:2.0\r\nEND:VCALENDAR\r\n"))
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if len(events) != 0 {
		t.Errorf("got %d events, want 0", len(events))
	}
}

// A feed with no UID still needs a stable id, or every refresh would look like
// a brand-new set of events.
func TestICSEvent_StableIDWithoutUID(t *testing.T) {
	body := "BEGIN:VCALENDAR\r\nBEGIN:VEVENT\r\nDTSTART:20260913T201500Z\r\nSUMMARY:No UID\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n"
	first := parseOrFail(t, body)[0].StableID("feed-1")
	second := parseOrFail(t, body)[0].StableID("feed-1")
	if first == "" {
		t.Fatal("StableID returned empty")
	}
	if first != second {
		t.Errorf("StableID is not stable: %q vs %q", first, second)
	}
}

// Two feeds containing the same UID must not collide into one event.
func TestICSEvent_StableIDIsScopedToItsFeed(t *testing.T) {
	e := parseOrFail(t, sampleICS)[0]
	if e.StableID("feed-1") == e.StableID("feed-2") {
		t.Error("same UID in different feeds produced the same id")
	}
}