"use strict";

/** @const */
var PIC_LOG_VERBOSE = false;

/**
 * Programmable Interrupt Controller
 * http://stanislavs.org/helppc/8259.html
 *
 * @constructor
 * @param {CPU} cpu
 * @param {PIC=} master
 */
function PIC(cpu, master)
{
    /**
     * all irqs off
     * @type {number}
     */
    this.irq_mask = 0;

    /**
     * @type {number}
     *
     * Bogus default value (both master and slave mapped to 0).
     * Will be initialized by the BIOS
     */
    this.irq_map = 0;

    /**
     * in-service register
     * Holds interrupts that are currently being serviced
     * @type {number}
     */
    this.isr = 0;

    /**
     * interrupt request register
     * Holds interrupts that have been requested
     * @type {number}
     */
    this.irr = 0;

    this.irq_value = 0;

    /**
     * @type {number}
     */
    this.requested_irq = -1;

    this.master = master;
    this.is_master = this.master === undefined;
    this.slave = undefined;

    this.name = this.is_master ? "master" : "slave ";

    this.expect_icw4 = false;
    this.state = 0;
    this.read_isr = 0;
    this.auto_eoi = 1;
    this.special_mask_mode = 0;

    this.elcr = 0;

    this.cpu = cpu;

    // Checking for callable interrupts:
    // (cpu changes interrupt flag) -> cpu.handle_irqs -> pic.check_irqs -> cpu.pic_call_irq
    // (pic changes isr/irr) -> cpu.handle_irqs -> ...

    // triggering irqs:
    // (io device has irq) -> cpu.device_raise_irq -> pic.set_irq -> cpu.handle_irqs -> (see above)


    if(this.is_master)
    {
        this.slave = new PIC(this.cpu, this);

        this.check_irqs = function()
        {
            if(this.requested_irq >= 0)
            {
                PIC_LOG_VERBOSE && dbg_log("master> Already requested irq: " + this.requested_irq, LOG_PIC);
                this.cpu.handle_irqs();
                return;
            }

            var enabled_irr = this.irr & this.irq_mask;

            if(!enabled_irr)
            {
                if(PIC_LOG_VERBOSE)
                {
                    dbg_log("master> no unmasked irrs. irr=" + h(this.irr, 2) +
                            " mask=" + h(this.irq_mask & 0xff, 2) + " isr=" + h(this.isr, 2), LOG_PIC);
                }
                return;
            }

            var irq_mask = enabled_irr & -enabled_irr;
            var special_mask = this.special_mask_mode ? this.irq_mask : -1;

            if(this.isr && (this.isr & -this.isr & special_mask) <= irq_mask)
            {
                // wait for eoi of higher or same priority interrupt
                dbg_log("master> higher prio: isr=" + h(this.isr, 2) +
                        " mask=" + h(this.irq_mask & 0xff, 2) + " irq=" + h(irq_mask, 2), LOG_PIC);
                return;
            }

            dbg_assert(irq_mask !== 0);
            var irq_number = v86util.int_log2_byte(irq_mask);
            dbg_assert(irq_mask === (1 << irq_number));

            PIC_LOG_VERBOSE && dbg_log("master> request irq " + irq_number, LOG_PIC);

            this.requested_irq = irq_number;
            this.cpu.handle_irqs();
        };

        this.acknowledge_irq = function()
        {
            if(this.requested_irq === -1)
            {
                return;
            }

            if(this.irr === 0)
            {
                PIC_LOG_VERBOSE && dbg_log("master> spurious requested=" + this.requested_irq, LOG_PIC);
                this.requested_irq = -1;
                //this.cpu.pic_call_irq(this.irq_map | 7);
                return;
            }
            dbg_assert(this.irr); // spurious
            dbg_assert(this.requested_irq >= 0);

            var irq_mask = 1 << this.requested_irq;

            if((this.elcr & irq_mask) === 0) // not in level mode
            {
                this.irr &= ~irq_mask;
            }

            if(!this.auto_eoi)
            {
                this.isr |= irq_mask;
            }

            PIC_LOG_VERBOSE && dbg_log("master> acknowledge " + this.requested_irq, LOG_PIC);
            if(this.requested_irq === 2)
            {
                this.slave.acknowledge_irq();
            }
            else
            {
                this.cpu.pic_call_irq(this.irq_map | this.requested_irq);
            }

            this.requested_irq = -1;
            this.check_irqs();
        };
    }
    else
    {
        // is slave
        this.check_irqs = function()
        {
            if(this.requested_irq >= 0)
            {
                PIC_LOG_VERBOSE && dbg_log("slave > Already requested irq: " + this.requested_irq, LOG_PIC);
                this.cpu.handle_irqs();
                return;
            }

            var enabled_irr = this.irr & this.irq_mask;

            if(!enabled_irr)
            {
                if(PIC_LOG_VERBOSE)
                {
                    dbg_log("slave > no unmasked irrs. irr=" + h(this.irr, 2) +
                            " mask=" + h(this.irq_mask & 0xff, 2) + " isr=" + h(this.isr, 2), LOG_PIC);
                }
                return;
            }

            var irq_mask = enabled_irr & -enabled_irr;
            var special_mask = this.special_mask_mode ? this.irq_mask : -1;

            if(this.isr && (this.isr & -this.isr & special_mask) <= irq_mask)
            {
                // wait for eoi of higher or same priority interrupt
                PIC_LOG_VERBOSE && dbg_log("slave > higher prio: isr=" + h(this.isr, 2) + " irq=" + h(irq_mask, 2), LOG_PIC);
                return;
            }

            dbg_assert(irq_mask !== 0);
            var irq_number = v86util.int_log2_byte(irq_mask);
            dbg_assert(irq_mask === (1 << irq_number));

            PIC_LOG_VERBOSE && dbg_log("slave > request irq " + irq_number, LOG_PIC);
            this.requested_irq = irq_number;
            this.master.set_irq(2);
        };

        this.acknowledge_irq = function()
        {
            if(this.requested_irq === -1)
            {
                return;
            }

            if(this.irr === 0)
            {
                PIC_LOG_VERBOSE && dbg_log("slave > spurious requested=" + this.requested_irq, LOG_PIC);
                this.requested_irq = -1;
                this.master.irq_value &= ~(1 << 2);
                this.cpu.pic_call_irq(this.irq_map | 7);
                return;
            }

            dbg_assert(this.irr); // spurious
            dbg_assert(this.requested_irq >= 0);

            var irq_mask = 1 << this.requested_irq;

            if((this.elcr & irq_mask) === 0) // not in level mode
            {
                this.irr &= ~irq_mask;
            }

            if(!this.auto_eoi)
            {
                this.isr |= irq_mask;
            }

            this.master.irq_value &= ~(1 << 2);
            PIC_LOG_VERBOSE && dbg_log("slave > acknowledge " + this.requested_irq, LOG_PIC);
            this.cpu.pic_call_irq(this.irq_map | this.requested_irq);

            this.requested_irq = -1;
            this.check_irqs();
        };
    }

    this.dump = function()
    {
        dbg_log("mask: " + h(this.irq_mask & 0xFF), LOG_PIC);
        dbg_log("base: " + h(this.irq_map), LOG_PIC);
        dbg_log("requested: " + h(this.irr), LOG_PIC);
        dbg_log("serviced: " + h(this.isr), LOG_PIC);

        if(this.is_master)
        {
            this.slave.dump();
        }
    };

    var io_base;
    var iobase_high;
    if(this.is_master)
    {
        io_base = 0x20;
        iobase_high = 0x4D0;
    }
    else
    {
        io_base = 0xA0;
        iobase_high = 0x4D1;
    }

    this.cpu.io.register_write(io_base, this, this.port20_write);
    this.cpu.io.register_read(io_base, this, this.port20_read);

    this.cpu.io.register_write(io_base | 1, this, this.port21_write);
    this.cpu.io.register_read(io_base | 1, this, this.port21_read);

    this.cpu.io.register_write(iobase_high, this, this.port4D0_write);
    this.cpu.io.register_read(iobase_high, this, this.port4D0_read);


    if(this.is_master)
    {
        this.set_irq = function(irq_number)
        {
            dbg_assert(irq_number >= 0 && irq_number < 16);

            if(irq_number >= 8)
            {
                this.slave.set_irq(irq_number - 8);
                return;
            }

            var irq_mask = 1 << irq_number;
            if((this.irq_value & irq_mask) === 0)
            {
                if(PIC_LOG_VERBOSE)
                {
                    dbg_log("master> set irq " + irq_number, LOG_PIC);
                }

                this.irr |= irq_mask;
                this.irq_value |= irq_mask;
                this.check_irqs();
            }
            else
            {
                if(PIC_LOG_VERBOSE)
                {
                    dbg_log("master> set irq " + irq_number + ": already set!", LOG_PIC);
                }
            }
        };

        this.clear_irq = function(irq_number)
        {
            dbg_assert(irq_number >= 0 && irq_number < 16);
            if(PIC_LOG_VERBOSE)
            {
                dbg_log("master> clear irq " + irq_number, LOG_PIC);
            }

            if(irq_number >= 8)
            {
                this.slave.clear_irq(irq_number - 8);
                return;
            }

            var irq_mask = 1 << irq_number;
            if(this.irq_value & irq_mask)
            {
                this.irq_value &= ~irq_mask;
                this.irr &= ~irq_mask;
                this.check_irqs();
            }
        };
    }
    else
    {
        this.set_irq = function(irq_number)
        {
            dbg_assert(irq_number >= 0 && irq_number < 8);

            var irq_mask = 1 << irq_number;
            if((this.irq_value & irq_mask) === 0)
            {
                if(PIC_LOG_VERBOSE)
                {
                    dbg_log("slave > set irq " + irq_number, LOG_PIC);
                }

                this.irr |= irq_mask;
                this.irq_value |= irq_mask;
                this.check_irqs();
            }
            else
            {
                if(PIC_LOG_VERBOSE)
                {
                    dbg_log("slave > set irq " + irq_number + ": already set!", LOG_PIC);
                }
            }
        };

        this.clear_irq = function(irq_number)
        {
            dbg_assert(irq_number >= 0 && irq_number < 8);
            if(PIC_LOG_VERBOSE)
            {
                dbg_log("slave > clear irq " + irq_number, LOG_PIC);
            }

            var irq_mask = 1 << irq_number;
            if(this.irq_value & irq_mask)
            {
                this.irq_value &= ~irq_mask;
                this.irr &= ~irq_mask;
                this.check_irqs();
            }
        };
    }

    this.get_isr = function()
    {
        return this.isr;
    };
}

PIC.prototype.get_state = function()
{
    var state = [];

    state[0] = this.irq_mask;
    state[1] = this.irq_map;
    state[2] = this.isr;
    state[3] = this.irr;
    state[4] = this.is_master;
    state[5] = this.slave;
    state[6] = this.expect_icw4;
    state[7] = this.state;
    state[8] = this.read_isr;
    state[9] = this.auto_eoi;
    state[10] = this.elcr;

    return state;
};

PIC.prototype.set_state = function(state)
{
    this.irq_mask = state[0];
    this.irq_map = state[1];
    this.isr = state[2];
    this.irr = state[3];
    this.is_master = state[4];
    this.slave && this.slave.set_state(state[5]);
    this.expect_icw4 = state[6];
    this.state = state[7];
    this.read_isr = state[8];
    this.auto_eoi = state[9];
    this.elcr = state[10];
};

PIC.prototype.port20_write = function(data_byte)
{
    //dbg_log("20 write: " + h(data_byte), LOG_PIC);
    if(data_byte & 0x10) // xxxx1xxx
    {
        // icw1
        dbg_log("icw1 = " + h(data_byte), LOG_PIC);
        this.isr = 0;
        this.irr = 0;
        this.irq_mask = 0;
        this.irq_value = 0;
        this.auto_eoi = 1;
        this.requested_irq = -1;

        this.expect_icw4 = data_byte & 1;
        this.state = 1;
    }
    else if(data_byte & 8) // xxx01xxx
    {
        // ocw3
        dbg_log("ocw3: " + h(data_byte), LOG_PIC);
        if(data_byte & 2)
        {
            this.read_isr = data_byte & 1;
        }
        if(data_byte & 4)
        {
            dbg_assert(false, "unimplemented: polling", LOG_PIC);
        }
        if(data_byte & 0x40)
        {
            this.special_mask_mode = (data_byte & 0x20) === 0x20;
            dbg_log("special mask mode: " + this.special_mask_mode, LOG_PIC);
        }
    }
    else // xxx00xxx
    {
        // ocw2
        // end of interrupt
        dbg_log("eoi: " + h(data_byte) + " (" + this.name + ")", LOG_PIC);

        var eoi_type = data_byte >> 5;

        if(eoi_type === 1)
        {
            // non-specific eoi
            this.isr &= this.isr - 1;
            dbg_log("new isr: " + h(this.isr, 2), LOG_PIC);
        }
        else if(eoi_type === 3)
        {
            // specific eoi
            this.isr &= ~(1 << (data_byte & 7));
        }
        else if((data_byte & 0xC8) === 0xC0)
        {
            // os2 v4
            let priority = data_byte & 7;
            dbg_log("lowest priority: " + h(priority), LOG_PIC);
        }
        else
        {
            dbg_log("Unknown eoi: " + h(data_byte), LOG_PIC);
            dbg_assert(false);
            this.isr &= this.isr - 1;
        }

        this.check_irqs();
    }
};

PIC.prototype.port20_read = function()
{
    if(this.read_isr)
    {
        dbg_log("read port 20h (isr): " + h(this.isr), LOG_PIC);
        return this.isr;
    }
    else
    {
        dbg_log("read port 20h (irr): " + h(this.irr), LOG_PIC);
        return this.irr;
    }
};

PIC.prototype.port21_write = function(data_byte)
{
    //dbg_log("21 write: " + h(data_byte), LOG_PIC);
    if(this.state === 0)
    {
        if(this.expect_icw4)
        {
            // icw4
            this.expect_icw4 = false;
            this.auto_eoi = data_byte & 2;
            dbg_log("icw4: " + h(data_byte) + " autoeoi=" + this.auto_eoi, LOG_PIC);

            if((data_byte & 1) === 0)
            {
                dbg_assert(false, "unimplemented: not 8086 mode", LOG_PIC);
            }
        }
        else
        {
            // ocw1
            this.irq_mask = ~data_byte;

            if(PIC_LOG_VERBOSE)
            {
                dbg_log("interrupt mask: " + (this.irq_mask & 0xFF).toString(2) +
                        " (" + this.name + ")", LOG_PIC);
            }

            this.check_irqs();
        }
    }
    else if(this.state === 1)
    {
        // icw2
        this.irq_map = data_byte;
        dbg_log("interrupts are mapped to " + h(this.irq_map) +
                " (" + this.name + ")", LOG_PIC);
        this.state++;
    }
    else if(this.state === 2)
    {
        // icw3
        this.state = 0;
        dbg_log("icw3: " + h(data_byte), LOG_PIC);
    }
};

PIC.prototype.port21_read = function()
{
    dbg_log("21h read " + h(~this.irq_mask & 0xff), LOG_PIC);
    return ~this.irq_mask & 0xFF;
};

PIC.prototype.port4D0_read = function()
{
    dbg_log("elcr read: " + h(this.elcr, 2), LOG_PIC);
    return this.elcr;
};

PIC.prototype.port4D0_write = function(value)
{
    dbg_log("elcr write: " + h(value, 2), LOG_PIC);
    // set by seabios to 00 0C (only set for pci interrupts)
    this.elcr = value;
};