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

// ponytail: Mapper 180 (Nichibutsu / Crazy Climber)
// Fixed first 16KB at $8000-$BFFF, switchable 16KB at $C000-$FFFF via write to $8000-$FFFF.
pub const Mapper180 = @This();

prg_bank: u8 = 0,
mirroring_mode: Mirroring,

pub fn init(initial_mirroring: Mirroring) Mapper180 {
    return .{ .mirroring_mode = initial_mirroring };
}

pub fn cpuRead(self: *const Mapper180, address: u16, prg_rom: []const u8, prg_ram: []const u8) ?u8 {
    if (address >= 0x6000 and address <= 0x7fff) {
        const offset = address - 0x6000;
        if (offset < prg_ram.len) return prg_ram[offset];
        return 0;
    }
    if (address >= 0x8000 and address <= 0xffff) {
        const total_16k_banks = @max(1, prg_rom.len / 0x4000);
        var bank: usize = 0;

        if (address < 0xc000) {
            bank = 0;
            const offset = address - 0x8000;
            if (offset < prg_rom.len) return prg_rom[offset];
        } else {
            bank = @as(usize, self.prg_bank) % total_16k_banks;
            const offset = (bank * 0x4000) + (address - 0xc000);
            if (offset < prg_rom.len) return prg_rom[offset];
        }
        return 0;
    }
    return null;
}

pub fn cpuWrite(self: *Mapper180, address: u16, value: u8, prg_ram: []u8) bool {
    if (address >= 0x6000 and address <= 0x7fff) {
        const offset = address - 0x6000;
        if (offset < prg_ram.len) {
            prg_ram[offset] = value;
            return true;
        }
        return false;
    }
    if (address >= 0x8000 and address <= 0xffff) {
        self.prg_bank = value & 0x0f;
        return true;
    }
    return false;
}

pub fn ppuRead(_: *const Mapper180, address: u16, chr_rom: []const u8, chr_ram: []const u8, chr_is_ram: bool) ?u8 {
    if (address < 0x2000) {
        if (chr_is_ram) {
            if (address < chr_ram.len) return chr_ram[address];
        } else if (chr_rom.len > 0) {
            if (address < chr_rom.len) return chr_rom[address];
        }
        return 0;
    }
    return null;
}

pub fn ppuWrite(_: *Mapper180, address: u16, value: u8, chr_ram: []u8, chr_is_ram: bool) bool {
    if (address < 0x2000 and chr_is_ram) {
        if (address < chr_ram.len) {
            chr_ram[address] = value;
            return true;
        }
    }
    return false;
}

pub fn mirroring(self: *const Mapper180) Mirroring {
    return self.mirroring_mode;
}

pub fn irqLine(_: *const Mapper180) bool {
    return false;
}

pub fn notifyPpuAddress(_: *Mapper180, _: u16) void {}

test "mapper180 bank switching" {
    var m = Mapper180.init(.horizontal);
    var ram: [0x2000]u8 = undefined;

    _ = m.cpuWrite(0x8000, 3, &ram);
    try std.testing.expectEqual(@as(u8, 3), m.prg_bank);
}