138 lines
4.1 KiB
Go
138 lines
4.1 KiB
Go
package moreser
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// NormalizePage 规范化分页参数，限制单次请求数量避免大分页拖垮 MongoDB。
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func NormalizePage(pageNum, pageSize, defaultPageSize, maxPageSize int64) (int64, int64) {
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if pageNum <= 0 {
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pageNum = 1
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}
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if pageSize <= 0 {
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pageSize = defaultPageSize
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}
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if pageSize > maxPageSize {
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pageSize = maxPageSize
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}
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return pageNum, pageSize
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}
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// InsertedAdsCount 计算实际可穿插的广告数量，每 interval 条内容后插入 1 条广告。
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func InsertedAdsCount(contentTotal, adsTotal, interval int64) int64 {
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if contentTotal <= 0 || adsTotal <= 0 || interval <= 0 {
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return 0
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}
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insertSlots := contentTotal / interval
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if insertSlots > adsTotal {
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return adsTotal
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}
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return insertSlots
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}
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// ContentPosition 计算内容原始下标在混排列表中的全局位置。
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func ContentPosition(contentIndex, adsTotal, interval int64) int64 {
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if interval <= 0 {
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return contentIndex
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}
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adsBefore := contentIndex / interval
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if adsBefore > adsTotal {
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adsBefore = adsTotal
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}
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return contentIndex + adsBefore
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}
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// FirstContentIndexAtOrAfter 找到指定混排位置之后第一条内容下标。
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func FirstContentIndexAtOrAfter(pos, contentTotal, adsTotal, interval int64) int64 {
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left, right := int64(0), contentTotal
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for left < right {
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mid := left + (right-left)/2
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if ContentPosition(mid, adsTotal, interval) < pos {
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left = mid + 1
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continue
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}
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right = mid
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}
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return left
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}
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// ContentRange 计算当前混排分页需要读取的内容下标范围。
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func ContentRange(start, end, contentTotal, adsTotal, interval int64) (int64, int64) {
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contentStart := FirstContentIndexAtOrAfter(start, contentTotal, adsTotal, interval)
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contentEnd := FirstContentIndexAtOrAfter(end, contentTotal, adsTotal, interval)
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if contentStart >= contentEnd {
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return 0, 0
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}
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return contentStart, contentEnd - contentStart
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}
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// ContentRangeWithoutTotal 计算当前混排分页需要读取的内容范围，不依赖内容总数。
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// 适用于列表接口不返回 totalCount 的场景；广告位仍按“每 interval 条内容后插入 1 条广告”计算。
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func ContentRangeWithoutTotal(start, end, adsTotal, interval int64) (int64, int64) {
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if start < 0 || end <= start {
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return 0, 0
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}
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contentStart := contentIndexAtMixedPosition(start, adsTotal, interval)
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contentEnd := contentIndexAtMixedPosition(end, adsTotal, interval)
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if contentStart >= contentEnd {
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return 0, 0
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}
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return contentStart, contentEnd - contentStart
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}
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// ContentIndexAtPositionWithoutTotal 计算混排位置对应的内容下标，不判断该位置是否为广告。
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func ContentIndexAtPositionWithoutTotal(pos, adsTotal, interval int64) int64 {
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return contentIndexAtMixedPosition(pos, adsTotal, interval)
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}
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// AdIndexAtPositionWithoutTotal 计算混排位置对应的广告下标，返回 -1 表示该位置不是广告。
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func AdIndexAtPositionWithoutTotal(pos, adsTotal, interval int64) int64 {
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if adsTotal <= 0 || interval <= 0 || pos < 0 {
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return -1
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}
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cycle := interval + 1
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if pos >= adsTotal*cycle {
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return -1
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}
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if pos%cycle != interval {
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return -1
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}
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return pos / cycle
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}
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// contentIndexAtMixedPosition 返回混排位置之前已经出现的内容数量。
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func contentIndexAtMixedPosition(pos, adsTotal, interval int64) int64 {
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if pos <= 0 {
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return 0
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}
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if adsTotal <= 0 || interval <= 0 {
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return pos
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}
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adCycle := interval + 1
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adAreaSize := adsTotal * adCycle
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if pos >= adAreaSize {
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return pos - adsTotal
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}
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fullCycles := pos / adCycle
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remain := pos % adCycle
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return fullCycles*interval + minInt64(remain, interval)
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}
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func minInt64(a, b int64) int64 {
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if a < b {
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return a
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}
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return b
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}
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// AdIndexAtPosition 计算混排位置对应的广告下标，返回 -1 表示该位置不是广告。
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func AdIndexAtPosition(pos, contentTotal, adsTotal, interval int64) int64 {
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if interval <= 0 {
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return -1
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}
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nextContent := FirstContentIndexAtOrAfter(pos+1, contentTotal, adsTotal, interval)
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prevContent := nextContent - 1
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if prevContent >= 0 && (prevContent+1)%interval == 0 && (prevContent+1)/interval-1 < adsTotal {
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if ContentPosition(prevContent, adsTotal, interval)+1 == pos {
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return (prevContent+1)/interval - 1
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}
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}
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return -1
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}
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