Origins + more test suite passing (#7)

# Description

This PR gets all the testsuite tests passing.

However, that is currently using an arena allocator, and if we instead
use a GPA we find that we're leaking memory. Need to fix this (and in
doing so figure out a good lifetime model)

TOUR.md

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+# Tour
+
+`biscuit-zig` is split into a number of modules. The following description should provide helpful orientation:
+
+- `biscuit-schema`
+  - Contains the `schema.proto` from the official biscuit repo
+  - Contains `schema.pb.zig` which is generated from `schema.proto` using https://github.com/Arwalk/zig-protobuf. This powers the biscuit deserialization.
+- `biscuit-format`
+  - Provides an intermediate `SerializedBiscuit` type that deserializes the protobuf format and verifies biscuit.
+- `biscuit`
+  - Provides runtime representation of biscuit, this is the main interface a consumer of the library will use.
+  - A `Biscuit` can be initialized

biscuit-builder/README.md

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+# biscuit-parser

biscuit-builder/build.zig

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+const std = @import("std");
+
+// Although this function looks imperative, note that its job is to
+// declaratively construct a build graph that will be executed by an external
+// runner.
+pub fn build(b: *std.Build) void {
+    // Standard target options allows the person running `zig build` to choose
+    // what target to build for. Here we do not override the defaults, which
+    // means any target is allowed, and the default is native. Other options
+    // for restricting supported target set are available.
+    const target = b.standardTargetOptions(.{});
+
+    // Standard optimization options allow the person running `zig build` to select
+    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
+    // set a preferred release mode, allowing the user to decide how to optimize.
+    const optimize = b.standardOptimizeOption(.{});
+
+    const schema = b.dependency("biscuit-schema", .{ .target = target, .optimize = optimize });
+    const format = b.dependency("biscuit-format", .{ .target = target, .optimize = optimize });
+    const datalog = b.dependency("biscuit-datalog", .{ .target = target, .optimize = optimize });
+
+    _ = b.addModule("biscuit-builder", .{
+        .root_source_file = .{ .path = "src/root.zig" },
+        .imports = &.{
+            .{ .name = "biscuit-schema", .module = schema.module("biscuit-schema") },
+            .{ .name = "biscuit-format", .module = format.module("biscuit-format") },
+            .{ .name = "biscuit-datalog", .module = datalog.module("biscuit-datalog") },
+        },
+    });
+
+    // Creates a step for unit testing. This only builds the test executable
+    // but does not run it.
+    const lib_unit_tests = b.addTest(.{
+        .root_source_file = .{ .path = "src/main.zig" },
+        .target = target,
+        .optimize = optimize,
+    });
+    lib_unit_tests.root_module.addImport("biscuit-schema", schema.module("biscuit-schema"));
+    lib_unit_tests.root_module.addImport("biscuit-format", format.module("biscuit-format"));
+
+    const run_lib_unit_tests = b.addRunArtifact(lib_unit_tests);
+
+    // Similar to creating the run step earlier, this exposes a `test` step to
+    // the `zig build --help` menu, providing a way for the user to request
+    // running the unit tests.
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_lib_unit_tests.step);
+}

biscuit-builder/build.zig.zon

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+.{
+    .name = "biscuit-builder",
+    // This is a [Semantic Version](https://semver.org/).
+    // In a future version of Zig it will be used for package deduplication.
+    .version = "0.0.0",
+
+    // This field is optional.
+    // This is currently advisory only; Zig does not yet do anything
+    // with this value.
+    //.minimum_zig_version = "0.11.0",
+
+    // This field is optional.
+    // Each dependency must either provide a `url` and `hash`, or a `path`.
+    // `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
+    // Once all dependencies are fetched, `zig build` no longer requires
+    // internet connectivity.
+    .dependencies = .{
+        // See `zig fetch --save <url>` for a command-line interface for adding dependencies.
+        //.example = .{
+        //    // When updating this field to a new URL, be sure to delete the corresponding
+        //    // `hash`, otherwise you are communicating that you expect to find the old hash at
+        //    // the new URL.
+        //    .url = "https://example.com/foo.tar.gz",
+        //
+        //    // This is computed from the file contents of the directory of files that is
+        //    // obtained after fetching `url` and applying the inclusion rules given by
+        //    // `paths`.
+        //    //
+        //    // This field is the source of truth; packages do not come from a `url`; they
+        //    // come from a `hash`. `url` is just one of many possible mirrors for how to
+        //    // obtain a package matching this `hash`.
+        //    //
+        //    // Uses the [multihash](https://multiformats.io/multihash/) format.
+        //    .hash = "...",
+        //
+        //    // When this is provided, the package is found in a directory relative to the
+        //    // build root. In this case the package's hash is irrelevant and therefore not
+        //    // computed. This field and `url` are mutually exclusive.
+        //    .path = "foo",
+        //},
+        .@"biscuit-schema" = .{ .path = "../biscuit-schema" },
+        .@"biscuit-format" = .{ .path = "../biscuit-format" },
+        .@"biscuit-datalog" = .{ .path = "../biscuit-datalog" },
+    },
+
+    // Specifies the set of files and directories that are included in this package.
+    // Only files and directories listed here are included in the `hash` that
+    // is computed for this package.
+    // Paths are relative to the build root. Use the empty string (`""`) to refer to
+    // the build root itself.
+    // A directory listed here means that all files within, recursively, are included.
+    .paths = .{
+        // This makes *all* files, recursively, included in this package. It is generally
+        // better to explicitly list the files and directories instead, to insure that
+        // fetching from tarballs, file system paths, and version control all result
+        // in the same contents hash.
+        "",
+        // For example...
+        //"build.zig",
+        //"build.zig.zon",
+        //"src",
+        //"LICENSE",
+        //"README.md",
+    },
+}

biscuit-builder/src/check.zig

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+const std = @import("std");
+const datalog = @import("biscuit-datalog");
+const Predicate = @import("predicate.zig").Predicate;
+const Term = @import("term.zig").Term;
+const Rule = @import("rule.zig").Rule;
+
+pub const Check = struct {
+    kind: datalog.Check.Kind,
+    queries: std.ArrayList(Rule),
+
+    pub fn deinit(check: Check) void {
+        for (check.queries.items) |query| {
+            query.deinit();
+        }
+
+        check.queries.deinit();
+    }
+
+    pub fn convert(check: Check, allocator: std.mem.Allocator, symbols: *datalog.SymbolTable) !datalog.Check {
+        var queries = std.ArrayList(datalog.Rule).init(allocator);
+
+        for (check.queries.items) |query| {
+            try queries.append(try query.convert(allocator, symbols));
+        }
+
+        return .{ .kind = check.kind, .queries = queries };
+    }
+
+    pub fn format(check: Check, comptime _: []const u8, _: std.fmt.FormatOptions, writer: anytype) !void {
+        try writer.print("check ", .{});
+
+        switch (check.kind) {
+            .one => try writer.print("if", .{}),
+            .all => try writer.print("all", .{}),
+        }
+
+        for (check.queries.items) |query| {
+            try writer.print(" {any}", .{query});
+        }
+    }
+};

biscuit-builder/src/date.zig

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+const std = @import("std");
+
+pub const Date = struct {
+    year: i32,
+    month: u8,
+    day: u8,
+    hour: u8,
+    minute: u8,
+    second: u8,
+    nanosecond: u32,
+    // Timezone offset in minutes from UTC; can be negative
+    utc_offset: i32,
+
+    pub fn eql(left: Date, right: Date) bool {
+        return left.year == right.year and
+            left.month == right.month and
+            left.day == right.day and
+            left.hour == right.hour and
+            left.minute == right.minute and
+            left.second == right.second and
+            left.nanosecond == right.nanosecond;
+    }
+
+    pub fn lt(left: Date, right: Date) bool {
+        if (left.year < right.year) return true;
+        if (left.year > right.year) return false;
+
+        std.debug.assert(left.year == right.year);
+
+        if (left.month < right.month) return true;
+        if (left.month > right.month) return false;
+
+        std.debug.assert(left.month == right.month);
+
+        if (left.day < right.day) return true;
+        if (left.day > right.day) return false;
+
+        std.debug.assert(left.day == right.day);
+
+        if (left.hour < right.hour) return true;
+        if (left.hour > right.hour) return false;
+
+        std.debug.assert(left.hour == right.hour);
+
+        if (left.minute < right.minute) return true;
+        if (left.minute > right.minute) return false;
+
+        std.debug.assert(left.minute == right.minute);
+
+        if (left.second < right.second) return true;
+        if (left.second > right.second) return false;
+
+        std.debug.assert(left.second == right.second);
+
+        if (left.nanosecond < right.nanosecond) return true;
+        if (left.nanosecond > right.nanosecond) return false;
+
+        std.debug.assert(left.nanosecond == right.nanosecond);
+
+        return false;
+    }
+
+    pub fn gt(left: Date, right: Date) bool {
+        if (left.year > right.year) return true;
+        if (left.year < right.year) return false;
+
+        std.debug.assert(left.year == right.year);
+
+        if (left.month > right.month) return true;
+        if (left.month < right.month) return false;
+
+        std.debug.assert(left.month == right.month);
+
+        if (left.day > right.day) return true;
+        if (left.day < right.day) return false;
+
+        std.debug.assert(left.day == right.day);
+
+        if (left.hour > right.hour) return true;
+        if (left.hour < right.hour) return false;
+
+        std.debug.assert(left.hour == right.hour);
+
+        if (left.minute > right.minute) return true;
+        if (left.minute < right.minute) return false;
+
+        std.debug.assert(left.minute == right.minute);
+
+        if (left.second > right.second) return true;
+        if (left.second < right.second) return false;
+
+        std.debug.assert(left.second == right.second);
+
+        if (left.nanosecond > right.nanosecond) return true;
+        if (left.nanosecond < right.nanosecond) return false;
+
+        std.debug.assert(left.nanosecond == right.nanosecond);
+
+        return false;
+    }
+
+    pub fn lteq(left: Date, right: Date) bool {
+        return left.eq(right) or left.lt(right);
+    }
+
+    pub fn gteq(left: Date, right: Date) bool {
+        return left.eq(right) or left.gt(right);
+    }
+
+    pub fn format(date: Date, comptime _: []const u8, _: std.fmt.FormatOptions, writer: anytype) !void {
+        return writer.print("{}-{}-{}T{}:{}:{}Z", .{ date.year, date.month, date.day, date.hour, date.minute, date.second });
+    }
+
+    // FIXME: leap seconds?
+    pub fn unixEpoch(date: Date) u64 {
+        var total_days: usize = 0;
+
+        const date_year = @as(usize, @intCast(date.year));
+
+        for (1970..date_year) |year| {
+            if (isLeapYear(usize, year)) {
+                total_days += 366;
+            } else {
+                total_days += 365;
+            }
+        }
+
+        for (1..date.month) |month| {
+            total_days += daysInMonth(usize, date_year, @as(u8, @intCast(month)));
+        }
+
+        for (1..date.day) |_| {
+            total_days += 1;
+        }
+
+        var total_seconds: u64 = total_days * 24 * 60 * 60;
+
+        total_seconds += @as(u64, date.hour) * 60 * 60;
+        total_seconds += @as(u64, date.minute) * 60;
+        total_seconds += date.second;
+
+        return total_seconds;
+    }
+
+    pub fn isDayMonthYearValid(comptime T: type, year: T, month: u8, day: u8) bool {
+        return switch (month) {
+            // 30 days has september, april june and november
+            4, 6, 9, 11 => day <= 30,
+            1, 3, 5, 7, 8, 10, 12 => day <= 31,
+            2 => if (isLeapYear(T, year)) day <= 29 else day <= 28,
+            else => false,
+        };
+    }
+};
+
+pub fn daysInMonth(comptime T: type, year: T, month: u8) u8 {
+    return switch (month) {
+        4, 6, 9, 11 => 30,
+        1, 3, 5, 7, 8, 10, 12 => 31,
+        2 => if (isLeapYear(T, year)) 29 else 28,
+        else => unreachable,
+    };
+}
+
+fn isLeapYear(comptime T: type, year: T) bool {
+    if (@mod(year, 400) == 0) return true;
+    if (@mod(year, 100) == 0) return false;
+    if (@mod(year, 4) == 0) return true;
+
+    return false;
+}