#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include "image_proc.h"
#include "user_proc.h"

#pragma pack(push,1)
typedef struct {
    uint16_t bfType;
    uint32_t bfSize;
    uint16_t bfReserved1;
    uint16_t bfReserved2;
    uint32_t bfOffBits;
} BMPFILEHEADER;
#pragma pack(pop)

static uint8_t*     g_pixels = NULL;
static BITMAPINFO*  g_bmi    = NULL;
static int g_w=0, g_h=0, g_bpp=0;
static const char* g_title = "BMP Viewer";

static void FreeImage() {
    free(g_pixels); g_pixels = NULL;
    free(g_bmi);    g_bmi = NULL;
    g_w = g_h = g_bpp = 0;
}

static int LoadBMP(const char* path) {
    FreeImage();
    FILE* fp = fopen(path, "rb");
    if(!fp){ fprintf(stderr,"无法打开: %s\n", path); return 0; }

    BMPFILEHEADER fh;
    BITMAPINFOHEADER ih;
    if(fread(&fh,sizeof(fh),1,fp)!=1){ fclose(fp); return 0; }
    if(fh.bfType != 0x4D42){ fclose(fp); fprintf(stderr,"非BMP\n"); return 0; }
    if(fread(&ih,sizeof(ih),1,fp)!=1){ fclose(fp); return 0; }
    if(ih.biCompression != BI_RGB){ fclose(fp); fprintf(stderr,"仅支持未压缩 BI_RGB\n"); return 0; }
    if(!(ih.biBitCount==8 || ih.biBitCount==24 || ih.biBitCount==32)){
        fclose(fp); fprintf(stderr,"不支持位数: %u\n", ih.biBitCount); return 0;
    }

    g_w = ih.biWidth;
    g_h = ih.biHeight;
    g_bpp = ih.biBitCount;

    int bytesPerPixel = g_bpp / 8;
    int stride = ((g_w * bytesPerPixel + 3) / 4) * 4;
    size_t imgSize = (size_t)stride * g_h;

    uint32_t colors = 0;
    if(g_bpp == 8){
        colors = ih.biClrUsed ? ih.biClrUsed : 256;
        if(colors > 256) colors = 256;
    }
    size_t bmiSize = sizeof(BITMAPINFOHEADER) + colors * sizeof(RGBQUAD);
    g_bmi = (BITMAPINFO*)calloc(1, bmiSize);
    if(!g_bmi){ fclose(fp); return 0; }
    g_bmi->bmiHeader = ih; 

    if(g_bpp == 8){
        if(colors){
            size_t readPaletteBytes = colors * sizeof(RGBQUAD);
            if(fread(g_bmi->bmiColors, 1, readPaletteBytes, fp) != readPaletteBytes){
                for(uint32_t i=0;i<colors;i++){
                    g_bmi->bmiColors[i].rgbRed =
                    g_bmi->bmiColors[i].rgbGreen =
                    g_bmi->bmiColors[i].rgbBlue = (BYTE)i;
                }
            }
        } else {
        }
    }

    g_pixels = (uint8_t*)malloc(imgSize);
    if(!g_pixels){ fclose(fp); FreeImage(); return 0; }

    if(fseek(fp, (long)fh.bfOffBits, SEEK_SET)!=0){
        fclose(fp); FreeImage(); return 0;
    }
    if(fread(g_pixels,1,imgSize,fp)!=imgSize){
        fclose(fp); FreeImage(); fprintf(stderr,"像素读取失败\n"); return 0;
    }
    fclose(fp);

    if(g_bpp == 8){
        int isGray = 1;
        for(uint32_t i=0;i<colors;i++){
            BYTE r=g_bmi->bmiColors[i].rgbRed;
            BYTE g=g_bmi->bmiColors[i].rgbGreen;
            BYTE b=g_bmi->bmiColors[i].rgbBlue;
            if(!(r==g && g==b)){ isGray=0; break; }
        }
        if(!isGray){
            for(uint32_t i=0;i<colors;i++){
                g_bmi->bmiColors[i].rgbRed =
                g_bmi->bmiColors[i].rgbGreen =
                g_bmi->bmiColors[i].rgbBlue = (BYTE)i;
            }
        }
    }

    return 1;
}

static LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam){
    switch(msg){
    case WM_ERASEBKGND:
        return 1;
    case WM_PAINT:{
        PAINTSTRUCT ps;
        HDC hdc = BeginPaint(hWnd,&ps);
        if(g_pixels && g_bmi){
            int dstW = g_w * IMAGE_SCALE;
            int dstH = g_h * IMAGE_SCALE;
            SetStretchBltMode(hdc, COLORONCOLOR);
            StretchDIBits(
                hdc,
                0,0,dstW,dstH,
                0,0,g_w,g_h,
                g_pixels,
                g_bmi,
                DIB_RGB_COLORS,
                SRCCOPY
            );
        } else {
            TextOutA(hdc,10,10,"未加载BMP",12);
        }
        EndPaint(hWnd,&ps);
    } break;
    case WM_DESTROY:
        FreeImage();
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd,msg,wParam,lParam);
    }
    return 0;
}

int APIENTRY WinMain(HINSTANCE hInst,HINSTANCE hPrev,LPSTR lpCmdLine,int nShow){
    (void)hPrev; (void)lpCmdLine;
    if(!LoadBMP(BMP_PATH)){
        char msg[256];
        snprintf(msg,sizeof(msg),"加载失败: %s", BMP_PATH);
        MessageBoxA(NULL,msg,"错误",MB_OK|MB_ICONERROR);
    } else {
        g_title = BMP_PATH;

        GrayImage gray = {0};
        if(ExtractGray(g_pixels, g_w, g_h, g_bpp, &gray)){
            
            img_proc(&gray);//这里调用了图像处理函数

            BITMAPINFO *newBMI = NULL;
            uint8_t *newPixels = NULL;
            if(Build8BitDIB(&gray, &newBMI, &newPixels)){
                free(g_pixels);
                free(g_bmi);
                g_pixels = newPixels;
                g_bmi = newBMI;
                g_bpp = 8; 
            }
        }
        FreeGray(&gray);
    }

    const char* cls = "BMP_VIEWER_CLASS";
    WNDCLASSA wc = (WNDCLASSA){0};
    wc.lpfnWndProc   = WndProc;
    wc.hInstance     = hInst;
    wc.lpszClassName = cls;
    wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    if(!RegisterClassA(&wc)) return 0;

    int winW = g_w ? g_w * IMAGE_SCALE : 640;
    int winH = g_h ? g_h * IMAGE_SCALE : 480;

    RECT rc = {0,0, winW, winH};
    DWORD style = WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_MINIMIZEBOX;
    AdjustWindowRect(&rc, style, FALSE);

    HWND hWnd = CreateWindowExA(
        0, cls, g_title,
        style,
        CW_USEDEFAULT, CW_USEDEFAULT,
        rc.right - rc.left,
        rc.bottom - rc.top,
        NULL,NULL,hInst,NULL);
    if(!hWnd) return 0;

    ShowWindow(hWnd,nShow);
    UpdateWindow(hWnd);

    MSG msg;
    while(GetMessage(&msg,NULL,0,0)>0){
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return (int)msg.wParam;
}