Move query helpers into common code

src/api/services/common.zig

@@ -0,0 +1,16 @@
+const std = @import("std");
+const util = @import("util");
+
+pub const Direction = enum {
+    ascending,
+    descending,
+
+    pub const jsonStringify = util.jsonSerializeEnumAsString;
+};
+
+pub const PageDirection = enum {
+    forward,
+    backward,
+
+    pub const jsonStringify = util.jsonSerializeEnumAsString;
+};

src/api/services/communities.zig

@@ -2,6 +2,7 @@ const std = @import("std");
 const builtin = @import("builtin");
 const util = @import("util");
 const sql = @import("sql");
+const common = @import("./common.zig");
 
 const Uuid = util.Uuid;
 const DateTime = util.DateTime;
@@ -153,20 +154,8 @@ pub const QueryArgs = struct {
         pub const jsonStringify = util.jsonSerializeEnumAsString;
     };
 
-    pub const Direction = enum {
-        ascending,
-        descending,
-
-        pub const jsonStringify = util.jsonSerializeEnumAsString;
-    };
-
-    pub const PageDirection = enum {
-        forward,
-        backward,
-
-        pub const jsonStringify = util.jsonSerializeEnumAsString;
-    };
-
+    pub const Direction = common.Direction;
+    pub const PageDirection = common.PageDirection;
     pub const Prev = std.meta.Child(std.meta.fieldInfo(QueryArgs, .prev).field_type);
     pub const OrderVal = std.meta.fieldInfo(Prev, .order_val).field_type;
 
@@ -211,30 +200,6 @@ pub const QueryResult = struct {
     next_page: QueryArgs,
 };
 
-const QueryBuilder = struct {
-    array: std.ArrayList(u8),
-    where_clauses_appended: usize = 0,
-
-    pub fn init(alloc: std.mem.Allocator) QueryBuilder {
-        return QueryBuilder{ .array = std.ArrayList(u8).init(alloc) };
-    }
-
-    pub fn deinit(self: *const QueryBuilder) void {
-        self.array.deinit();
-    }
-
-    pub fn andWhere(self: *QueryBuilder, clause: []const u8) !void {
-        if (self.where_clauses_appended == 0) {
-            try self.array.appendSlice("WHERE ");
-        } else {
-            try self.array.appendSlice(" AND ");
-        }
-
-        try self.array.appendSlice(clause);
-        self.where_clauses_appended += 1;
-    }
-};
-
 const max_max_items = 100;
 
 pub const QueryError = error{
@@ -246,7 +211,7 @@ pub const QueryError = error{
 // arguments.
 // `args.max_items` is only a request, and fewer entries may be returned.
 pub fn query(db: anytype, args: QueryArgs, alloc: std.mem.Allocator) !QueryResult {
-    var builder = QueryBuilder.init(alloc);
+    var builder = sql.QueryBuilder.init(alloc);
     defer builder.deinit();
 
     try builder.array.appendSlice(
@@ -266,21 +231,21 @@ pub fn query(db: anytype, args: QueryArgs, alloc: std.mem.Allocator) !QueryResul
     if (args.prev) |prev| {
         if (prev.order_val != args.order_by) return error.PageArgMismatch;
 
-        try builder.andWhere(switch (args.order_by) {
-            .name => "(name, id)",
-            .host => "(host, id)",
-            .created_at => "(created_at, id)",
-        });
-        _ = try builder.array.appendSlice(switch (args.direction) {
+        switch (args.order_by) {
+            .name => try builder.andWhere("(name, id)"),
+            .host => try builder.andWhere("(host, id)"),
+            .created_at => try builder.andWhere("(created_at, id)"),
+        }
+        switch (args.direction) {
             .ascending => switch (args.page_direction) {
-                .forward => " > ",
-                .backward => " < ",
+                .forward => try builder.andWhere(" > "),
+                .backward => try builder.andWhere(" < "),
             },
             .descending => switch (args.page_direction) {
-                .forward => " < ",
-                .backward => " > ",
+                .forward => try builder.andWhere(" < "),
+                .backward => try builder.andWhere(" > "),
             },
-        });
+        }
 
         _ = try builder.array.appendSlice("($5, $6)");
     }

src/sql/lib.zig

@@ -25,6 +25,47 @@ pub const Engine = enum {
     sqlite,
 };
 
+/// Helper for building queries at runtime. All constituent parts of the
+/// query should be defined at comptime, however the choice of whether
+/// or not to include them can occur at runtime.
+pub const QueryBuilder = struct {
+    array: std.ArrayList(u8),
+    where_clauses_appended: usize = 0,
+
+    pub fn init(alloc: std.mem.Allocator) QueryBuilder {
+        return QueryBuilder{ .array = std.ArrayList(u8).init(alloc) };
+    }
+
+    pub fn deinit(self: *const QueryBuilder) void {
+        self.array.deinit();
+    }
+
+    /// Add a chunk of sql to the query without processing
+    pub fn appendSlice(self: *QueryBuilder, comptime sql: []const u8) !void {
+        try self.array.appendSlice(sql);
+    }
+
+    /// Add a where clause to the query. Clauses are assumed to be components
+    /// in an overall expression in Conjunctive Normal Form (AND of OR's).
+    /// https://en.wikipedia.org/wiki/Conjunctive_normal_form
+    /// All calls to andWhere must be contiguous, that is, they cannot be
+    /// interspersed with calls to appendSlice
+    pub fn andWhere(self: *QueryBuilder, comptime clause: []const u8) !void {
+        if (self.where_clauses_appended == 0) {
+            try self.array.appendSlice("WHERE ");
+        } else {
+            try self.array.appendSlice(" AND ");
+        }
+
+        try self.array.appendSlice(clause);
+        self.where_clauses_appended += 1;
+    }
+
+    pub fn str(self: *const QueryBuilder) []const u8 {
+        return self.array.items;
+    }
+};
+
 // TODO: make this suck less
 pub const Config = union(Engine) {
     postgres: struct {