const std = @import("std");
const Allocator = std.mem.Allocator;
const ArenaAllocator = std.heap.ArenaAllocator;

/// Config is the main config struct. These fields map directly to the
/// CLI flag names hence we use a lot of `@""` syntax to support hyphens.
pub const Config = struct {
    /// Font size
    @"font-size": u8 = 14,

    /// Background color for the window.
    background: Color = .{ .r = 0, .g = 0, .b = 0 },

    /// Foreground color for the window.
    foreground: Color = .{ .r = 0xFF, .g = 0xA5, .b = 0 },

    /// The command to run, usually a shell. If this is not an absolute path,
    /// it'll be looked up in the PATH.
    command: ?[]const u8 = null,

    /// Additional configuration files to read.
    @"config-file": RepeatableString = .{},

    /// This is set by the CLI parser for deinit.
    _arena: ?ArenaAllocator = null,

    pub fn deinit(self: *Config) void {
        if (self._arena) |arena| arena.deinit();
        self.* = undefined;
    }
};

/// Color represents a color using RGB.
pub const Color = struct {
    r: u8,
    g: u8,
    b: u8,

    pub const Error = error{
        InvalidFormat,
    };

    pub fn parseCLI(input: ?[]const u8) !Color {
        return fromHex(input orelse return error.ValueRequired);
    }

    /// fromHex parses a color from a hex value such as #RRGGBB. The "#"
    /// is optional.
    pub fn fromHex(input: []const u8) !Color {
        // Trim the beginning '#' if it exists
        const trimmed = if (input.len != 0 and input[0] == '#') input[1..] else input;

        // We expect exactly 6 for RRGGBB
        if (trimmed.len != 6) return Error.InvalidFormat;

        // Parse the colors two at a time.
        var result: Color = undefined;
        comptime var i: usize = 0;
        inline while (i < 6) : (i += 2) {
            const v: u8 =
                ((try std.fmt.charToDigit(trimmed[i], 16)) * 16) +
                try std.fmt.charToDigit(trimmed[i + 1], 16);

            @field(result, switch (i) {
                0 => "r",
                2 => "g",
                4 => "b",
                else => unreachable,
            }) = v;
        }

        return result;
    }

    test "fromHex" {
        const testing = std.testing;

        try testing.expectEqual(Color{ .r = 0, .g = 0, .b = 0 }, try Color.fromHex("#000000"));
        try testing.expectEqual(Color{ .r = 10, .g = 11, .b = 12 }, try Color.fromHex("#0A0B0C"));
        try testing.expectEqual(Color{ .r = 10, .g = 11, .b = 12 }, try Color.fromHex("0A0B0C"));
        try testing.expectEqual(Color{ .r = 255, .g = 255, .b = 255 }, try Color.fromHex("FFFFFF"));
    }
};

/// RepeatableString is a string value that can be repeated to accumulate
/// a list of strings. This isn't called "StringList" because I find that
/// sometimes leads to confusion that it _accepts_ a list such as
/// comma-separated values.
pub const RepeatableString = struct {
    const Self = @This();

    // Allocator for the list is the arena for the parent config.
    list: std.ArrayListUnmanaged([]const u8) = .{},

    pub fn parseCLI(self: *Self, alloc: Allocator, input: ?[]const u8) !void {
        const value = input orelse return error.ValueRequired;
        try self.list.append(alloc, value);
    }

    test "parseCLI" {
        const testing = std.testing;
        var arena = ArenaAllocator.init(testing.allocator);
        defer arena.deinit();
        const alloc = arena.allocator();

        var list: Self = .{};
        try list.parseCLI(alloc, "A");
        try list.parseCLI(alloc, "B");

        try testing.expectEqual(@as(usize, 2), list.list.items.len);
    }
};

test {
    std.testing.refAllDecls(@This());
}