hugo/hugolib/pageSort.go

// Copyright © 2014 Steve Francia <spf@spf13.com>.
//
// Licensed under the Simple Public License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://opensource.org/licenses/Simple-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package hugolib

import (
    "sort"
)

/*
 * Implementation of a custom sorter for Pages
 */

// A type to implement the sort interface for Pages
type PageSorter struct {
    pages Pages
    by    PageBy
}

// Closure used in the Sort.Less method.
type PageBy func(p1, p2 *Page) bool

func (by PageBy) Sort(pages Pages) {
    ps := &PageSorter{
        pages: pages,
        by:    by, // The Sort method's receiver is the function (closure) that defines the sort order.
    }
    sort.Sort(ps)
}

var DefaultPageSort = func(p1, p2 *Page) bool {
    if p1.Weight == p2.Weight {
        return p1.Date.Unix() > p2.Date.Unix()
    } else {
        return p1.Weight < p2.Weight
    }
}

func (ps *PageSorter) Len() int      { return len(ps.pages) }
func (ps *PageSorter) Swap(i, j int) { ps.pages[i], ps.pages[j] = ps.pages[j], ps.pages[i] }

// Less is part of sort.Interface. It is implemented by calling the "by" closure in the sorter.
func (ps *PageSorter) Less(i, j int) bool { return ps.by(ps.pages[i], ps.pages[j]) }

func (p Pages) Sort() {
    PageBy(DefaultPageSort).Sort(p)
}

func (p Pages) Limit(n int) Pages {
    if len(p) < n {
        return p[0:n]
    } else {
        return p
    }
}

func (p Pages) ByWeight() Pages {
    PageBy(DefaultPageSort).Sort(p)
    return p
}

func (p Pages) ByDate() Pages {
    date := func(p1, p2 *Page) bool {
        return p1.Date.Unix() < p2.Date.Unix()
    }

    PageBy(date).Sort(p)
    return p
}

func (p Pages) ByLength() Pages {
    length := func(p1, p2 *Page) bool {
        return len(p1.Content) < len(p2.Content)
    }

    PageBy(length).Sort(p)
    return p
}

func (p Pages) Reverse() Pages {
    for i, j := 0, len(p)-1; i < j; i, j = i+1, j-1 {
        p[i], p[j] = p[j], p[i]
    }

    return p
}