package templates

import "fmt"
import "strconv"
import "strings"

// CalendarSummary is one calendar (own or shared) shown in the combined
// month view's legend.
type CalendarSummary struct {
	Ref      string // path-safe reference: "name" or "owner~name"
	Name     string
	Owner    string // owner's username
	Color    string // hex color like "#3b82f6", "" if unset
	Shared   bool   // true if owned by someone other than the viewer
	Writable bool
	Virtual  bool // true for computed calendars (e.g. birthdays) with no import/export
}

// EventSummary is a single event shown inside a month-view day cell.
type EventSummary struct {
	ID       string
	CalRef   string
	Color    string
	Summary  string
	TimeText string // e.g. "14:00" or "" for all-day events
	AllDay   bool
	// LinkURL overrides the default "/web/calendar/{CalRef}/{ID}/edit"
	// link target, used by virtual/read-only calendars (e.g. birthdays)
	// that don't have an editable event object of their own.
	LinkURL string
}

// MonthDay is one day cell in the month grid.
type MonthDay struct {
	Date    string // "YYYY-MM-DD", used for links and the "new event" date
	Day     int    // day-of-month number shown in the cell
	InMonth bool   // false for the leading/trailing days of neighboring months
	IsToday bool
	Events  []EventSummary
}

// MonthViewData is everything the combined month grid template needs to
// render one month across every calendar (own + shared) visible to the
// viewer.
type MonthViewData struct {
	Calendars    []CalendarSummary
	HasWritable  bool // true if the viewer can create events in at least one calendar
	MonthLabel   string // e.g. "August 2026"
	Weeks        [][]MonthDay
	PrevMonthURL string
	NextMonthURL string
	TodayURL     string
}

// CalendarOption is one entry in the "new event" calendar <select>.
type CalendarOption struct {
	Ref   string
	Label string
}

// EventFormData pre-fills the create/edit event form.
type EventFormData struct {
	CalRef        string // resolved/fixed calendar reference (edit), or the selected one (new)
	CalendarLabel string // fixed, read-only display label used when editing
	Calendars     []CalendarOption // populated only for new-event forms
	Writable      bool             // false when editing an event in a read-only shared calendar
	ID            string           // empty when creating a new event
	Summary       string
	Description   string
	Location      string
	AllDay        bool
	StartDate     string // "YYYY-MM-DD"
	StartTime     string // "HH:MM", empty when AllDay
	EndDate       string // "YYYY-MM-DD"
	EndTime       string // "HH:MM", empty when AllDay
}

templ MonthView(username string, data MonthViewData) {
	@Layout("Calendar", username) {
		<div class="flex items-center justify-between mb-6 gap-4 flex-wrap">
			<h1 class="text-2xl font-semibold">Calendar</h1>
			<div class="flex gap-2 items-center flex-wrap">
				<a href={ templ.URL(data.PrevMonthURL) } class="bg-white border border-gray-300 rounded-md px-3 py-1.5 text-sm font-medium text-gray-700 hover:bg-gray-50">&larr;</a>
				<a href={ templ.URL(data.TodayURL) } class="bg-white border border-gray-300 rounded-md px-3 py-1.5 text-sm font-medium text-gray-700 hover:bg-gray-50">Today</a>
				<a href={ templ.URL(data.NextMonthURL) } class="bg-white border border-gray-300 rounded-md px-3 py-1.5 text-sm font-medium text-gray-700 hover:bg-gray-50">&rarr;</a>
				<span class="text-lg font-medium ml-2">{ data.MonthLabel }</span>
				if data.HasWritable {
					<a href="/web/calendar/new"
						class="bg-indigo-600 text-white rounded-md px-3 py-1.5 text-sm font-medium hover:bg-indigo-700 ml-2">
						New event
					</a>
				}
			</div>
		</div>

		if len(data.Calendars) == 0 {
			<p class="text-sm text-gray-500 mb-6">
				You don't have any calendars yet — create one from the
				<a href="/web/" class="text-indigo-600 hover:underline">dashboard</a> first.
			</p>
		} else {
			<div class="grid grid-cols-7 gap-px bg-gray-200 border border-gray-200 rounded-lg overflow-hidden text-sm mb-6">
				for _, wd := range weekdayLabels() {
					<div class="bg-gray-50 px-2 py-1.5 font-medium text-gray-500 text-xs text-center">{ wd }</div>
				}
				for _, week := range data.Weeks {
					for _, day := range week {
						@monthDayCell(day)
					}
				}
			</div>

			<div class="bg-white rounded-lg border border-gray-200 divide-y divide-gray-200">
				for _, c := range data.Calendars {
					@calendarLegendRow(c)
				}
			</div>
		}
	}
}

templ calendarLegendRow(c CalendarSummary) {
	<div class="px-4 py-3 flex items-center gap-3 text-sm flex-wrap">
		<span class="w-3 h-3 rounded-full shrink-0 ring-1 ring-inset ring-black/10" style={ "background-color: " + colorOrDefault(c.Color) }></span>
		<span class="font-medium">{ c.Name }</span>
		if c.Shared {
			<span class="text-xs text-gray-500">shared by { c.Owner }</span>
		}
		if !c.Writable {
			<span class="text-xs text-gray-400">(read-only)</span>
		}
		<span class="flex-1"></span>
		if !c.Virtual {
			<a href={ templ.URL("/web/calendar/" + c.Ref + "/export") } class="text-indigo-600 hover:underline text-xs">Export .ics</a>
		}
		if c.Writable {
			<form method="POST" action={ templ.URL("/web/calendar/" + c.Ref + "/import") } enctype="multipart/form-data" class="flex items-center gap-1">
				<input type="file" name="file" accept=".ics,text/calendar" required class="text-xs"/>
				<button type="submit" class="text-indigo-600 hover:underline text-xs">Import</button>
			</form>
		}
	</div>
}

templ monthDayCell(day MonthDay) {
	<div class={ "bg-white min-h-[6rem] p-1.5 flex flex-col gap-1", templ.KV("bg-gray-50 text-gray-400", !day.InMonth) }>
		<div class="flex items-center justify-between">
			<a
				href={ templ.URL("/web/calendar/new?date=" + day.Date) }
				class={ "text-xs font-medium rounded-full w-5 h-5 flex items-center justify-center", templ.KV("bg-indigo-600 text-white", day.IsToday), templ.KV("hover:bg-gray-100", !day.IsToday) }
				title="New event"
			>
				{ fmt.Sprint(day.Day) }
			</a>
		</div>
		for _, ev := range day.Events {
			<a
				href={ templ.URL(eventLinkURL(ev)) }
				class="block truncate rounded px-1.5 py-0.5 text-xs hover:opacity-80"
				style={ "background-color: " + colorOrDefault(ev.Color) + "22; color: " + eventTextColor(ev.Color) }
				title={ ev.Summary }
			>
				<span class="inline-block w-1.5 h-1.5 rounded-full mr-1 ring-1 ring-inset ring-black/10" style={ "background-color: " + eventTextColor(ev.Color) }></span>
				if !ev.AllDay && ev.TimeText != "" {
					<span class="font-medium">{ ev.TimeText }</span>
				}
				{ " " + ev.Summary }
			</a>
		}
	</div>
}

func eventLinkURL(ev EventSummary) string {
	if ev.LinkURL != "" {
		return ev.LinkURL
	}
	return "/web/calendar/" + ev.CalRef + "/" + ev.ID + "/edit"
}

// eventTextColor returns a color derived from hex, darkened if needed so
// it stays legible as text on monthDayCell's very light (~13% opacity)
// tinted event background. Without this, a light calendar color like
// white or pale yellow renders its own event text as invisible or
// near-invisible, since the same color is used for both the tint and the
// text. Colors that are already dark enough are returned unchanged.
func eventTextColor(hex string) string {
	c := colorOrDefault(hex)
	r, g, b, ok := parseHexColor(c)
	if !ok {
		return c
	}
	// Perceived luminance (ITU-R BT.601).
	luminance := 0.299*float64(r) + 0.587*float64(g) + 0.114*float64(b)
	const maxReadableLuminance = 170
	if luminance <= maxReadableLuminance {
		return c
	}
	// Scale each channel down so the color darkens towards black while
	// keeping its hue, ending up comfortably below the threshold.
	scale := maxReadableLuminance / luminance * 0.75
	return fmt.Sprintf("#%02x%02x%02x", clampByte(float64(r)*scale), clampByte(float64(g)*scale), clampByte(float64(b)*scale))
}

// parseHexColor parses a "#rrggbb" string into its red/green/blue
// components. ok is false for anything else (including 3-digit shorthand
// hex, which colorOrDefault/hexColorRe never produce).
func parseHexColor(s string) (r, g, b int, ok bool) {
	s = strings.TrimPrefix(s, "#")
	if len(s) != 6 {
		return 0, 0, 0, false
	}
	v, err := strconv.ParseInt(s, 16, 32)
	if err != nil {
		return 0, 0, 0, false
	}
	return int(v >> 16 & 0xff), int(v >> 8 & 0xff), int(v & 0xff), true
}

func clampByte(v float64) int {
	if v < 0 {
		return 0
	}
	if v > 255 {
		return 255
	}
	return int(v)
}



templ EventForm(username string, data EventFormData, errMsg string) {
	@Layout("Calendar", username) {
		<a href="/web/calendar" class="text-sm text-indigo-600 hover:underline">&larr; Calendar</a>
		<h1 class="text-2xl font-semibold mt-2 mb-6">
			if data.ID == "" {
				New event
			} else {
				Edit event
			}
		</h1>
		if errMsg != "" {
			<p class="mb-4 text-sm text-red-600 bg-red-50 border border-red-200 rounded px-3 py-2">{ errMsg }</p>
		}
		if data.ID != "" && !data.Writable {
			<p class="mb-4 text-sm text-amber-700 bg-amber-50 border border-amber-200 rounded px-3 py-2">
				This calendar was shared with you as read-only — you can view this event but not change it.
			</p>
		}
		<form
			method="POST"
			action={ eventFormAction(data) }
			class="bg-white rounded-lg border border-gray-200 p-6 space-y-6 max-w-xl"
		>
			<fieldset disabled?={ data.ID != "" && !data.Writable } class="space-y-6">
			<div>
				<label class="block text-sm font-medium text-gray-700">Calendar</label>
				if data.ID == "" {
					<select name="calendar" class="mt-1 block w-full rounded-md border-gray-300 border px-3 py-2 shadow-sm">
						for _, c := range data.Calendars {
							<option value={ c.Ref } selected?={ c.Ref == data.CalRef }>{ c.Label }</option>
						}
					</select>
				} else {
					<p class="mt-1 text-sm text-gray-600">{ data.CalendarLabel }</p>
				}
			</div>

			<div>
				<label class="block text-sm font-medium text-gray-700">Title</label>
				<input name="summary" type="text" required value={ data.Summary }
					class="mt-1 block w-full rounded-md border-gray-300 border px-3 py-2 shadow-sm"/>
			</div>

			<label class="flex items-center gap-2 text-sm text-gray-700">
				<input id="all-day" name="all_day" type="checkbox" value="1" checked?={ data.AllDay }/>
				All-day event
			</label>

			<div class="grid grid-cols-2 gap-4">
				<div>
					<label class="block text-sm font-medium text-gray-700">Start date</label>
					<input name="start_date" type="date" required value={ data.StartDate }
						class="mt-1 block w-full rounded-md border-gray-300 border px-3 py-2 shadow-sm"/>
				</div>
				<div id="start-time-field" class={ templ.KV("hidden", data.AllDay) }>
					<label class="block text-sm font-medium text-gray-700">Start time</label>
					<input name="start_time" type="time" value={ data.StartTime }
						class="mt-1 block w-full rounded-md border-gray-300 border px-3 py-2 shadow-sm"/>
				</div>
				<div>
					<label class="block text-sm font-medium text-gray-700">End date</label>
					<input name="end_date" type="date" required value={ data.EndDate }
						class="mt-1 block w-full rounded-md border-gray-300 border px-3 py-2 shadow-sm"/>
				</div>
				<div id="end-time-field" class={ templ.KV("hidden", data.AllDay) }>
					<label class="block text-sm font-medium text-gray-700">End time</label>
					<input name="end_time" type="time" value={ data.EndTime }
						class="mt-1 block w-full rounded-md border-gray-300 border px-3 py-2 shadow-sm"/>
				</div>
			</div>

			<div>
				<label class="block text-sm font-medium text-gray-700">Location</label>
				<input name="location" type="text" value={ data.Location }
					class="mt-1 block w-full rounded-md border-gray-300 border px-3 py-2 shadow-sm"/>
			</div>
			<div>
				<label class="block text-sm font-medium text-gray-700">Description</label>
				<textarea name="description" rows="4"
					class="mt-1 block w-full rounded-md border-gray-300 border px-3 py-2 shadow-sm">{ data.Description }</textarea>
			</div>
			</fieldset>

			<div class="flex items-center justify-between pt-2">
				if data.ID == "" || data.Writable {
					<button type="submit" class="bg-indigo-600 text-white rounded-md px-4 py-2 text-sm font-medium hover:bg-indigo-700">
						Save
					</button>
				}
				if data.ID != "" && data.Writable {
					<form method="POST" action={ templ.URL("/web/calendar/" + data.CalRef + "/" + data.ID + "/delete") } onsubmit="return confirm('Delete this event?')">
						<button type="submit" class="text-red-600 hover:underline text-sm">Delete event</button>
					</form>
				}
				if data.ID != "" {
					<a href={ templ.URL("/web/calendar/" + data.CalRef + "/" + data.ID + "/export") } class="text-indigo-600 hover:underline text-sm">Export .ics</a>
				}
			</div>
		</form>

		<script type="module" src="/web/static/calendar.js"></script>
	}
}

func eventFormAction(data EventFormData) templ.SafeURL {
	if data.ID == "" {
		return templ.URL("/web/calendar/new")
	}
	return templ.URL("/web/calendar/" + data.CalRef + "/" + data.ID + "/edit")
}

func weekdayLabels() []string {
	return []string{"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"}
}