/*
    Plasma effect (chars)

    Combines sine waves to create a 2D pattern, maps to custom characters,
    and renders to the 40x30 character grid with intensity-based colors.

    code     : zbyti (conversion & optimizations)
    original : https://github.com/tebe6502/Mad-Pascal/blob/origin/samples/a8/demoeffects/plasma_2.pas
    date     : 2025.04.16
    platform : MicroW8 0.4.1
*/

include "../include/microw8-api.cwa"

//-----------------------------------------------------------------------------
// Constants defining memory layout, screen dimensions, and effect parameters
//-----------------------------------------------------------------------------

const MEM_END           = 0x40000;

const CUSTOM_FONT       = FONT + 0x100;
const CHARS             = 0x20;
const BASE_COLOR        = 0xF0;

const PI                = 3.14159265;
const RAD               = PI / 180.0;

const SCR_X             = 320;
const SCR_Y             = 240;
const SCR_W             = SCR_X / 8; // 40
const SCR_H             = SCR_Y / 8; // 30
const SCR_SIZE          = SCR_X * SCR_Y;

const SIN_TABLE_SIZE    = 128;                      // Number of entries in the sine lookup table
const SIN_TABLE_MASK    = SIN_TABLE_SIZE - 1;

const SIN_TABLE         = MEM_END - SIN_TABLE_SIZE; // Memory address for sine table
const ROW_BUFFER        = SIN_TABLE - SCR_W;        // Memory address for precomputed row buffer

//-----------------------------------------------------------------------------
// Global variables to track animation state
//-----------------------------------------------------------------------------

global mut phaseA = 1; // Phase offset for the first sine wave, controls animation
global mut phaseB = 5; // Phase offset for the second sine wave, controls animation

//-----------------------------------------------------------------------------

/*
    Logs a value to the console (STDOUT) with a prefix for debugging purposes

    Args:
      prefix : 4-character identifier (i32) to label the output
      log    : Integer value to log (i32)

    Prints to console and returns to screen output
*/
fn console(prefix: i32, log: i32) {
    printChar('\6');    // Switch output to console
    printChar(prefix);  // Print the prefix
    printInt(log);      // Print the integer value
    printChar('\n\4');  // Print newline and switch back to screen output
}

//-------------------------------------

/*
    Fills a sine table with precomputed values for fast lookups

    Args:
      adr  : Memory address where the sine table is stored
      size : Number of entries in the table

    Computes: sin(i * 180/size * radians) * 255 for i = 0 to size-1, scaled to 0-255
*/
fn fillSin(adr: i32, size: i32) {
    let i = 0;
    let inline f = 180.00 / size as f32 * RAD;
    loop i {
        (adr+i)?0 = (sin(f * i as f32) * 255.0) as i32;
        branch_if (i +:= 1) < size: i;
    }
}

//-----------------------------------------------------------------------------

/*
    Initialization function called when the program starts
*/
export fn start() {
    // Populate the sine table with values for fast wave calculations
    fillSin(SIN_TABLE, SIN_TABLE_SIZE);
}

//-------------------------------------

/*
    Update function called each frame to render the plasma effect
*/
export fn upd() {
    let pA = phaseA; // Local copy of phaseA to avoid modifying global during frame
    let pB = phaseB; // Local copy of phaseB for the same reason

    let i = 0;
    loop i {
        // Wrap phase values to stay within sine table bounds using bitwise AND
        pA &= SIN_TABLE_MASK;
        pB &= SIN_TABLE_MASK;

        // Combine two sine waves and store in row buffer
        i?ROW_BUFFER = pA?SIN_TABLE + pB?SIN_TABLE;

        pA += 3; // Shift phase for first sine wave (controls wave speed)
        pB += 7; // Shift phase for second sine wave (different speed for variety)

        branch_if (i +:= 1) < SCR_W: i;
    }

    i = 0;
    loop i {
        let j = 0;
        loop j {
            // Combine wave values from row buffer for current position
            // Use bitwise AND to clamp to 0-255, then scale to 0-15 for character index
            let c = ((j?ROW_BUFFER + i?ROW_BUFFER) & 255) >> 4;

            // Set text color based on intensity (base color + scaled value)
            setTextColor(BASE_COLOR + c);
            // Draw custom character corresponding to intensity
            printChar(CHARS + c);

            branch_if (j +:= 1) < SCR_W: j;
        }
        branch_if (i +:= 1) < SCR_H: i;
    }

    // Update global phase offsets for the next frame to animate the pattern
    phaseA += 0; // Increment phaseA to shift the pattern (+/- speed move)
    phaseB += 1; // Increment phaseB to shift the pattern (+/- right/left move)
}

//-----------------------------------------------------------------------------

/*
    Custom font data defining 16 characters (8x8 pixels each)
    Each character represents a different intensity level for the plasma effect
    Pixels range from empty (0x00) to nearly full (0xFE or 0x7F) to simulate gradients
*/
data CUSTOM_FONT {
    i8(
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x18, 0x18, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x38, 0x38, 0x38, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x3c, 0x3c, 0x3c, 0x3c, 0x00, 0x00,
        0x00, 0x7c, 0x7c, 0x7c, 0x7c, 0x7c, 0x00, 0x00,
        0x00, 0x7e, 0x7e, 0x7e, 0x7e, 0x7e, 0x7e, 0x00,
        0xfe, 0xfe, 0xfe, 0xfe, 0xfe, 0xfe, 0xfe, 0x00,
        0x00, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f,
        0x00, 0x7e, 0x7e, 0x7e, 0x7e, 0x7e, 0x7e, 0x00,
        0x00, 0x7c, 0x7c, 0x7c, 0x7c, 0x7c, 0x00, 0x00,
        0x00, 0x00, 0x3c, 0x3c, 0x3c, 0x3c, 0x00, 0x00,
        0x00, 0x00, 0x38, 0x38, 0x38, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x18, 0x18, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
    )
}