{{- /*
Inputs:
  archived       -> pages after rolling window
  rollingWindow  -> integer (from config)
  context        -> current page (.)
  basePath       -> e.g. "archive" or "archive/articles"
  homePath       -> optional
  extraMonths    -> optional slice of "YYYY/MM"
*/ -}}

{{- $archived := .archived | default (slice) -}}
{{- $context := .context -}}
{{- $basePath := trim (.basePath | default "archive") "/" -}}
{{- $homePath := .homePath | default site.Home.RelPermalink -}}
{{- $extraMonths := .extraMonths | default (slice) -}}

{{- /* -------------------------------------- */ -}}
{{- /* Build month list (HOME + real months) */ -}}
{{- /* -------------------------------------- */ -}}

{{- $months := slice -}}
{{- $months = $months | append "HOME" -}}

{{- /* From archived pages */ -}}
{{- if gt (len $archived) 0 -}}
  {{- $archivedGroups := $archived.GroupByDate "2006/01" -}}
  {{- range $archivedGroups -}}
    {{- if not (in $months .Key) -}}
      {{- $months = $months | append .Key -}}
    {{- end -}}
  {{- end -}}
{{- end -}}

{{- /* From extraMonths argument */ -}}
{{- range $extraMonths -}}
  {{- if and (ne . "HOME") (not (in $months .)) -}}
    {{- $months = $months | append . -}}
  {{- end -}}
{{- end -}}

{{- $validMonths := slice -}}
{{- $validMonths = $validMonths | append "HOME" -}}

{{- range $months -}}
  {{- if ne . "HOME" -}}

    {{- /* If this month came from extraMonths, always allow it */ -}}
    {{- if in $extraMonths . -}}
      {{- $validMonths = $validMonths | append . -}}
    {{- else -}}

      {{- $parts := split . "/" -}}
      {{- if eq (len $parts) 2 -}}
        {{- $year := index $parts 0 -}}
        {{- $month := index $parts 1 -}}

        {{- $p := site.GetPage (printf "%s/%s/%s" $basePath $year $month) -}}
        {{- if not $p -}}
          {{- $p = site.GetPage (printf "/%s/%s/%s" $basePath $year $month) -}}
        {{- end -}}

        {{- if $p -}}
          {{- $validMonths = $validMonths | append . -}}
        {{- end -}}
      {{- end -}}

    {{- end -}}

  {{- end -}}
{{- end -}}

{{- /* Separate HOME from real months */ -}}
{{- $realMonths := slice -}}

{{- range $validMonths -}}
  {{- if ne . "HOME" -}}
    {{- $realMonths = $realMonths | append . -}}
  {{- end -}}
{{- end -}}

{{- /* Sort descending (YYYY/MM works lexicographically) */ -}}
{{- $realMonths = sort $realMonths "value" "desc" -}}

{{- /* Rebuild months list */ -}}
{{- $months = slice -}}
{{- $months = $months | append "HOME" -}}

{{- range $realMonths -}}
  {{- $months = $months | append . -}}
{{- end -}}

{{- range $months -}}
  {{- if ne . "HOME" -}}

    {{- $parts := split . "/" -}}
    {{- if eq (len $parts) 2 -}}
      {{- $year := index $parts 0 -}}
      {{- $month := index $parts 1 -}}

      {{- $p := site.GetPage (printf "%s/%s/%s" $basePath $year $month) -}}
      {{- if not $p -}}
        {{- $p = site.GetPage (printf "/%s/%s/%s" $basePath $year $month) -}}
      {{- end -}}

      {{- if $p -}}
        {{- $validMonths = $validMonths | append . -}}
      {{- end -}}
    {{- end -}}

  {{- end -}}
{{- end -}}

{{- $total := len $months -}}

{{- if gt $total 1 -}}

  {{- /* -------------------------------------- */ -}}
  {{- /* Determine current index              */ -}}
  {{- /* -------------------------------------- */ -}}

  {{- $parts := split (trim $context.RelPermalink "/") "/" -}}
  {{- $currentIndex := 0 -}}

  {{- if gt (len $parts) 2 -}}
    {{- $year := index $parts (sub (len $parts) 2) -}}
    {{- $month := index $parts (sub (len $parts) 1) -}}
    {{- $currentKey := printf "%s/%s" $year $month -}}

    {{- range $i, $m := $months -}}
      {{- if eq $m $currentKey -}}
        {{- $currentIndex = $i -}}
      {{- end -}}
    {{- end -}}
  {{- end -}}
  

  {{- /* -------------------------------------- */ -}}
  {{- /* Sliding window (5 entries)           */ -}}
  {{- /* -------------------------------------- */ -}}

  {{- $window := 5 -}}
  {{- $start := sub $currentIndex 2 -}}
  {{- if lt $start 0 }}{{- $start = 0 -}}{{- end -}}

  {{- if gt (add $start $window) $total -}}
    {{- $start = sub $total $window -}}
    {{- if lt $start 0 }}{{- $start = 0 -}}{{- end -}}
  {{- end -}}

  {{- $end := add $start $window -}}
  {{- if gt $end $total }}{{- $end = $total -}}{{- end -}}

  <nav class="mt4">

    {{- /* << */ -}}
    {{- if gt $currentIndex 0 -}}
      <a href="{{- $homePath -}}">&laquo;</a> |
    {{- end -}}

    {{- /* < */ -}}
    {{- if gt $currentIndex 0 -}}
      {{- if eq $currentIndex 1 -}}
        <a href="{{- $homePath -}}">&lsaquo;</a> |
      {{- else -}}
        {{- $prev := index $months (sub $currentIndex 1) -}}
        {{- if eq $prev "HOME" -}}
          <a href="{{- $homePath -}}">&lsaquo;</a> |
        {{- else -}}
          <a href="/{{- $basePath -}}/{{- $prev -}}/">&lsaquo;</a> |
        {{- end -}}
      {{- end -}}
    {{- end -}}

    {{- /* Middle entries */ -}}
    {{- range $i := seq $start (sub $end 1) -}}
      {{- $key := index $months $i -}}

      {{- if eq $key "HOME" -}}
        {{- if eq $i $currentIndex -}}
          Newest
        {{- else -}}
          <a href="{{- $homePath -}}">Newest</a>
        {{- end -}}
      {{- else -}}
        {{- $date := time (printf "%s-01" (replace $key "/" "-")) -}}
        {{- if eq $i $currentIndex -}}
          {{- dateFormat "Jan 06" $date -}}
        {{- else -}}
          <a href="/{{- $basePath -}}/{{- $key -}}/">
            {{- dateFormat "Jan 06" $date -}}
          </a>
        {{- end -}}
      {{- end -}}

      {{- if lt $i (sub $end 1) -}} | {{- end -}}
    {{- end -}}

    {{- /* > */ -}}
    {{- if lt (add $currentIndex 1) $total -}}
      {{- $next := index $months (add $currentIndex 1) -}}
      | {{- if eq $next "HOME" -}}
        <a href="{{- $homePath -}}">&rsaquo;</a>
      {{- else -}}
        <a href="/{{- $basePath -}}/{{- $next -}}/">&rsaquo;</a>
      {{- end -}}
    {{- end -}}

    {{- /* >> */ -}}
    {{- if lt $currentIndex (sub $total 1) -}}
      {{- $last := index $months (sub $total 1) -}}
      | {{- if eq $last "HOME" -}}
        <a href="{{- $homePath -}}">&raquo;</a>
      {{- else -}}
        <a href="/{{- $basePath -}}/{{- $last -}}/">&raquo;</a>
      {{- end -}}
    {{- end -}}

  </nav>

{{- end -}}