fediglam/src/util/lib.zig

const std = @import("std");
const iters = @import("./iters.zig");

pub const ciutf8 = @import("./ciutf8.zig");
pub const Uuid = @import("./Uuid.zig");
pub const DateTime = @import("./DateTime.zig");
pub const Url = @import("./Url.zig");
pub const PathIter = iters.PathIter;
pub const QueryIter = iters.QueryIter;
pub const SqlStmtIter = iters.Separator(';');

/// Joins an array of strings, prefixing every entry with `prefix`,
/// and putting `separator` in between each pair
pub fn comptimeJoinWithPrefix(
    comptime separator: []const u8,
    comptime prefix: []const u8,
    comptime strs: []const []const u8,
) []const u8 {
    comptime {
        if (strs.len == 0) return "";

        var size: usize = 0;
        for (strs) |str| size += prefix.len + str.len + separator.len;
        size -= separator.len;

        var buf = std.mem.zeroes([size]u8);

        // can't use std.mem.join because of problems with comptime allocation
        // https://github.com/ziglang/zig/issues/5873#issuecomment-1001778218
        //var fba = std.heap.FixedBufferAllocator.init(&buf);
        //return (std.mem.join(fba.allocator(), separator, fields) catch unreachable) ++ " ";

        var buf_idx = 0;
        for (strs) |str, i| {
            std.mem.copy(u8, buf[buf_idx..], prefix);
            buf_idx += prefix.len;
            std.mem.copy(u8, buf[buf_idx..], str);
            buf_idx += str.len;

            if (i != strs.len - 1) {
                std.mem.copy(u8, buf[buf_idx..], separator);
                buf_idx += separator.len;
            }
        }

        return &buf;
    }
}

/// Joins an array of strings, putting `separator` in between each pair
pub fn comptimeJoin(
    comptime separator: []const u8,
    comptime strs: []const []const u8,
) []const u8 {
    return comptimeJoinWithPrefix(separator, "", strs);
}

/// Helper function to serialize a runtime enum value as a string inside JSON.
/// To use, add
/// ```
///      pub const jsonStringify = util.jsonSerializeEnumAsString;
/// ```
/// to your enum type.
pub fn jsonSerializeEnumAsString(
    enum_value: anytype,
    opt: std.json.StringifyOptions,
    writer: anytype,
) !void {
    switch (@typeInfo(@TypeOf(enum_value))) {
        .Enum => |info| if (!info.is_exhaustive) @compileError("Enum must be exhaustive"),
        .Pointer => |info| if (info.size == .One) {
            return jsonSerializeEnumAsString(enum_value.*, opt, writer);
        } else @compileError("Must be enum type or pointer to enum, got " ++ @typeName(@TypeOf(enum_value))),
        else => @compileError("Must be enum type or pointer to enum, got " ++ @typeName(@TypeOf(enum_value))),
    }

    return std.fmt.format(writer, "\"{s}\"", .{@tagName(enum_value)});
}

/// Recursively frees a struct/array/slice/etc using the given allocator
/// by freeing any slices or pointers inside. Assumes that every pointer-like
/// object within points to its own allocation that must be free'd separately.
/// Do *not* use on self-referential types or structs that contain duplicate
/// slices.
/// Meant to be the inverse of `deepClone` below
pub fn deepFree(alloc: ?std.mem.Allocator, val: anytype) void {
    const T = @TypeOf(val);
    switch (@typeInfo(T)) {
        .Pointer => |ptr| switch (ptr.size) {
            .One => {
                deepFree(alloc, val.*);
                alloc.?.destroy(val);
            },
            .Slice => {
                for (val) |v| deepFree(alloc, v);
                alloc.?.free(val);
            },
            else => @compileError("Many and C-style pointers not supported by deepfree"),
        },
        .Optional => if (val) |v| deepFree(alloc, v) else {},
        .Struct => |struct_info| inline for (struct_info.fields) |field| deepFree(alloc, @field(val, field.name)),
        .Union => |union_info| inline for (union_info.fields) |field| {
            const tag = @field(std.meta.Tag(T), field.name);
            if (@as(std.meta.Tag(T), val) == tag) {
                deepFree(alloc, @field(val, field.name));
            }
        },
        .ErrorUnion => if (val) |v| deepFree(alloc, v) else {},
        .Array => for (val) |v| deepFree(alloc, v),

        .Enum, .Int, .Float, .Bool, .Void, .Type => {},

        else => @compileError("Type " ++ @typeName(T) ++ " not supported by deepFree"),
    }
}

/// Clones a struct/array/slice/etc and all its submembers.
/// Assumes that there are no self-refrential pointers within and that
/// every pointer should be followed.
pub fn deepClone(alloc: std.mem.Allocator, val: anytype) !@TypeOf(val) {
    const T = @TypeOf(val);
    var result: T = undefined;
    switch (@typeInfo(T)) {
        .Pointer => |ptr| switch (ptr.size) {
            .One => {
                result = try alloc.create(ptr.child);
                errdefer alloc.free(result);
                result.* = try deepClone(alloc, val.*);
            },
            .Slice => {
                const slice = try alloc.alloc(ptr.child, val.len);
                errdefer alloc.free(slice);

                var count: usize = 0;
                errdefer for (slice[0..count]) |v| deepFree(alloc, v);

                for (val) |v, i| {
                    slice[i] = try deepClone(alloc, v);
                    count += 1;
                }

                result = slice;
            },
            else => @compileError("Many and C-style pointers not supported"),
        },
        .Optional => {
            result = if (val) |v| try deepClone(alloc, v) else null;
        },
        .Struct => {
            const fields = std.meta.fields(T);
            var count: usize = 0;
            errdefer {
                inline for (fields) |f, i| {
                    if (i < count) deepFree(alloc, @field(result, f.name));
                }
            }

            inline for (fields) |f| {
                @field(result, f.name) = try deepClone(alloc, @field(val, f.name));
                count += 1;
            }
        },
        .Union => {
            inline for (comptime std.meta.fieldNames(T)) |f| {
                if (std.meta.isTag(val, f)) {
                    return @unionInit(T, f, try deepClone(alloc, @field(val, f)));
                }
            } else unreachable;
        },
        .Array => {
            var count: usize = 0;
            errdefer for (result[0..count]) |v| deepFree(alloc, v);

            for (val) |v, i| {
                result[i] = try deepClone(alloc, v);
                count += 1;
            }
        },
        .Enum, .Int, .Float, .Bool, .Void, .Type => {
            result = val;
        },
        else => @compileError("Type " ++ @typeName(T) ++ " not supported"),
    }

    return result;
}

threadlocal var prng: ?std.rand.DefaultPrng = null;

pub fn getThreadPrng() std.rand.Random {
    if (prng) |*p| return p.random();

    @panic("Thread PRNG not seeded");
}

pub fn seedThreadPrng() !void {
    @setCold(true);

    var buf: [8]u8 = undefined;
    try std.os.getrandom(&buf);

    prng = std.rand.DefaultPrng.init(@bitCast(u64, buf));
}

pub const testing = struct {
    pub fn expectDeepEqual(expected: anytype, actual: @TypeOf(expected)) !void {
        const T = @TypeOf(expected);
        switch (@typeInfo(T)) {
            .Null, .Void => return,
            .Int, .Float, .Bool, .Enum => try std.testing.expectEqual(expected, actual),
            .Struct => {
                inline for (comptime std.meta.fieldNames(T)) |f| {
                    try expectDeepEqual(@field(expected, f), @field(actual, f));
                }
            },
            .Union => {
                inline for (comptime std.meta.fieldNames(T)) |f| {
                    if (std.meta.isTag(expected, f)) {
                        try std.testing.expect(std.meta.isTag(actual, f));
                        try expectDeepEqual(@field(expected, f), @field(actual, f));
                    }
                }
            },
            .Pointer, .Array => {
                if (comptime std.meta.trait.isIndexable(T)) {
                    try std.testing.expectEqual(expected.len, actual.len);
                    for (expected) |_, i| {
                        try expectDeepEqual(expected[i], actual[i]);
                    }
                } else if (comptime std.meta.trait.isSingleItemPtr(T)) {
                    try expectDeepEqual(expected.*, actual.*);
                }
            },
            .Optional => {
                if (expected) |e| {
                    try expectDeepEqual(e, actual orelse return error.TestExpectedEqual);
                } else {
                    try std.testing.expect(actual == null);
                }
            },
            else => @compileError("Unsupported Type " ++ @typeName(T)),
        }
    }
};