110 lines
2.7 KiB
D
110 lines
2.7 KiB
D
/**
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* Defines various components useful for paginated operations.
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*/
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module util.pagination;
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import handy_http_primitives;
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import std.conv;
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enum SortDir : string {
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ASC = "ASC",
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DESC = "DESC"
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}
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struct Sort {
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immutable string attribute;
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immutable SortDir dir;
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static Optional!Sort parse(string expr) {
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import std.string;
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string[] parts = expr.split(",");
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if (parts.length == 1) return Optional!Sort.of(Sort(parts[0], SortDir.ASC));
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if (parts.length != 2) return Optional!Sort.empty;
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string attr = parts[0];
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string dirExpr = parts[1];
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SortDir d;
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if (dirExpr == SortDir.ASC) {
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d = SortDir.ASC;
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} else if (dirExpr == SortDir.DESC) {
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d = SortDir.DESC;
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} else {
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return Optional!Sort.empty;
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}
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return Optional!Sort.of(Sort(attr, d));
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}
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}
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struct PageRequest {
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immutable uint page;
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immutable ushort size;
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immutable Sort[] sorts;
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bool isUnpaged() const {
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return page < 1;
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}
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static PageRequest unpaged() {
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return PageRequest(0, 0, []);
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}
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static PageRequest parse(in ServerHttpRequest request, PageRequest defaults) {
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import std.algorithm;
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import std.array;
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uint pg = request.getParamAs!uint("page", defaults.page);
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ushort sz = request.getParamAs!ushort("size", defaults.size);
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Sort[] s = request.queryParams
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.filter!(p => p.key == "sort" && p.values.length > 0)
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.map!(p => Sort.parse(p.values[0]))
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.filter!(o => !o.isNull)
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.map!(o => o.value)
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.array;
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return PageRequest(pg, sz, s.idup);
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}
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string toSql() const {
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import std.array;
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auto app = appender!string;
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if (sorts.length > 0) {
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app ~= "ORDER BY ";
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for (size_t i = 0; i < sorts.length; i++) {
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app ~= sorts[i].attribute;
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app ~= " ";
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app ~= cast(string) sorts[i].dir;
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if (i + 1 < sorts.length) app ~= ",";
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}
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app ~= " ";
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}
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app ~= "LIMIT ";
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app ~= size.to!string;
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app ~= " OFFSET ";
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app ~= page.to!string;
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return app[];
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}
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PageRequest next() const {
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if (isUnpaged) return this;
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return PageRequest(page + 1, size, sorts);
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}
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PageRequest prev() const {
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if (isUnpaged) return this;
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return PageRequest(page - 1, size, sorts);
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}
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}
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struct Page(T) {
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T[] items;
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PageRequest pageRequest;
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}
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Page!U mapItems(T, U)(in Page!T page, U function(const(T)) fn) {
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import std.algorithm : map;
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import std.array : array;
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return Page!U(
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page.items.map!fn.array,
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page.pageRequest
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);
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}
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