#include <cairo/cairo.h>
#include <pango/pangocairo.h>
#include <stdio.h>
#include <stdlib.h>

#include "color.h"

// struct for storing dimensions used for calculations, movement, etc.
struct dimensions {
   // Multiplication factors
   int row_count;	/* rows */
   int column_count;	/* columns */

   // All of these are in units chosen by width in "calp.c"
   // Most likely milimeters (mm)
   double paper_width; 	/* paper width */
   double paper_height;	/* paper height */
   double month_width;	/* month width */
   double month_height;	/* month height */
   double month_top_corner_x;
   double month_top_corner_y;
   double day_width;	/* day box width */
   double day_height;	/* day box height */
   double margin;	/* margin */
   double header_width;
   double header_height;
};

// struct to hold Month-specific info, like what day of the week the first
// day lands on, how many days are in the month, etc.
struct month_info {
   int month_position;
   int first_day;
   int num_of_days;
   int minimum_rows;
};


// struct for defining RGB colors
struct RGB {
   double r;
   double g;
   double b;
};



// Convert Hex color strings to their RGB counterparts.
// IMO, hex strings are easier to work with, so this is 
// a nice helper function.
struct RGB hex_to_rgb(char *str) {
   unsigned int r, g, b;
   struct RGB color;

   sscanf(str, "%02x%02x%02x", &r, &g, &b);
   
   color.r = (r / 255.0);
   color.g = (g / 255.0);
   color.b = (b / 255.0);

   return color;
}



// Set a context's color using a HEX code. Color macros are defined
// in color.h
int set_color(cairo_t *c, char *hex) {
   struct RGB color = hex_to_rgb(hex);
   cairo_set_source_rgb (c, color.r, color.g, color.b);
   return 0;
}


// Get the day of the week for a given day
// Used for calculating when the start of a month is
// Relative to "Su Mo Tu ... Sa" frame, not when Su and Sa are together
// Range is 0 -> 6
// https://wiki.c2.com/?PerpetualCalendarAlgorithm
int day_of_week (int d, int m, int y) {
   return((d += m < 3 ? y-- : y - 2, 23*m/9 + d + 4 + y/4- y/100 + y/400)%7);
}




// Fill entire background with current color 
// Function name is changed for clarity
int fill_bg(cairo_t *c) {
   cairo_paint(c);
   return 0;
}




// Needn't be a string pointer, can be fixed array of chars
// Requires Font Family (string) and Size (int)
// Creates and destroys layout within the scope of the function
// Is that performant when looped over 365 operations?
int draw_text (cairo_t *c, double x, double y, char *font_family, int font_size, char *text) {
   char font[100];

   // Concat font string for pango_font_description_from_string
   snprintf(font, sizeof(font), "%s %d", font_family, font_size);

   //Initialize Pango Stuff
   PangoLayout *layout;
   PangoFontDescription *desc;


   // Create a PangoLayout, setting font & text
   layout = pango_cairo_create_layout(c);
   desc = pango_font_description_from_string(font);
   pango_layout_set_font_description(layout, desc);
   pango_font_description_free(desc);

   pango_layout_set_alignment(layout, PANGO_ALIGN_CENTER);
   pango_layout_set_text(layout, text, -1);

   cairo_move_to (c, x, y);
   pango_cairo_show_layout (c, layout);
   g_object_unref(layout);
   return 0;
}


// Get the dimensions of a string of text
// Returns a PangoRectangle struct
PangoRectangle get_logical_extents (cairo_t *c, char *font_family, int font_size, char *text) {
   char font[100];

   // Concat font string for pango_font_description_from_string
   snprintf(font, sizeof(font), "%s %d", font_family, font_size);

   PangoLayout *layout;
   PangoFontDescription *desc;
   PangoRectangle rect;

   // Create a PangoLayout, setting font & text
   layout = pango_cairo_create_layout(c);
   desc = pango_font_description_from_string(font);
   pango_layout_set_font_description(layout, desc);
   pango_font_description_free(desc);

   pango_layout_set_text(layout, text, -1);
   pango_layout_get_pixel_extents(layout, &rect, NULL);
   //pango_layout_get_extents(layout, NULL, &rect);

   g_object_unref(layout);
   return(rect);
}



// Calculate dimenions for one page and stores it in the dimensions struct
// Used for determining where elements should be drawn on the page
int calculate_dimensions(double pw, double ph, struct dimensions *d) {
   d->row_count = 6;
   d->column_count = 7;

   // Percentage of page that should be margin
   double margin = 0.05 * pw;
   
   // width of day is 1/7th of total width
   double box_width = pw / 10.0;

   // Everything other than margin
   double month_width = box_width * d->column_count; 


   // Width = Height; Day Box is a square
   double box_height = box_width;

   // Height is based on how tall # of weeks are 
   double month_height = box_height * d->row_count;

   // Set items in struct to calculated values
   d->paper_width = pw;
   d->paper_height = ph;
   d->margin = margin;
   d->month_width = month_width;
   d->month_top_corner_x = (pw - (month_width)) / 2.0;
   d->month_top_corner_y = ph - margin - month_height;
   d->month_height = month_height;
   d->day_width = box_width;
   d->day_height = box_height;
   return 0;
}


// Print the contents of a dimensions struct. 
// Use for debugging
int print_dimensions(struct dimensions *d) {
   printf("row count:    %d\n", d->row_count);
   printf("column count:   %d\n", d->column_count);
   printf("paper width:    %.2f\n", d->paper_width);
   printf("paper height:   %.2f\n", d->paper_height);
   printf("margin:         %.2f\n", d->margin);
   printf("month width:    %.2f\n", d->month_width);
   printf("month height:   %.2f\n", d->month_height);
   printf("month_top_corner_x: %f\n", d->month_top_corner_x);
   printf("month_top_corner_y: %f\n", d->month_top_corner_y);
   printf("day width:      %.2f\n", d->day_width);
   printf("day height:     %.2f\n", d->day_height);
   //printf("header width:      %.2f\n", d->header_width);
   //printf("header height:     %.2f\n", d->header_height);
   return 0;
}



// Calculate minimum amount of rows a month can fit in.
// Most months can fit within 4 or 5 rows instead of 6.
// TBD: This can probably done in a more efficient way
int calculate_minimum_rows(struct month_info *m, struct dimensions *d) {
   int extra_rows = 0;
   
   int days_in_first_week = (d->column_count - m->first_day);

   if (m->first_day == 0) {
      days_in_first_week = m->first_day;
   }

   int days_in_last_week = (m->num_of_days - days_in_first_week) % 7;

   int middle_weeks = (m->num_of_days - days_in_first_week - days_in_last_week) / 7;

   if (days_in_first_week != 0) {
      extra_rows++;
   }

   if (days_in_last_week != 0) {
      extra_rows++;
   }

   int minimum_rows = middle_weeks + extra_rows;

   return minimum_rows;
}



// Draws the grid lines for a month
int draw_month_grid (cairo_t *c, struct month_info *m, struct dimensions *d) {
   double cursor_x = d->month_top_corner_x;

   int row_offset = d->row_count - calculate_minimum_rows(m, d);
   double cursor_y = d->month_top_corner_y + (row_offset * d->day_height);

   double x = cursor_x;
   double y = cursor_y;

   set_color(c, BLACK);
   cairo_set_line_width (c, 1.0);

   for (int i = 0; i <= d->column_count; i++) {
      cairo_move_to(c, cursor_x, cursor_y);
      cairo_line_to(c, cursor_x, cursor_y + (d->month_height - (row_offset * d->day_height)));
      cursor_x = cursor_x + d->day_width;
   }

   // Recenter the cursor
   cursor_x = x;
   cursor_y = y;

   for (int i = 0; i <= d->row_count; i++) {
      cairo_move_to(c, cursor_x, cursor_y);
      cairo_line_to(c, cursor_x + d->month_width, cursor_y);
      cursor_y = cursor_y + d->day_height;
   }

   cairo_stroke(c);
   return 0;
}



int construct_day_box(cairo_t *cd, int month, int day, int week_day) {
   char str[20];
   double padding = 8.0;

   set_color(cd, WHITE);
   fill_bg(cd);

   if ((month == 0) && (day == 1) && (week_day == 1)) {
   }
   
   // draw_text(), and therefore pango_layout_set_text(), needs a 
   // string as input, so the current day's date is converted.
   snprintf(str, sizeof(str), "%d", day);

   set_color(cd, BLACK);
   draw_text(cd, padding, padding, "Monospace", 15, str);
   return 0;
}



// Draws one month using daybox sub-surface & context, main context, and dimension struct
int draw_month (cairo_t *c, cairo_t *cd, cairo_surface_t *s, struct month_info *m, struct dimensions *d) {
   double cursor_x = d->month_top_corner_x;

   if (m->first_day != 0) cursor_x = cursor_x + (d->day_width * m->first_day);

   // Push bottom of month as far down the page as the margin allows 
   int row_offset = d->row_count - calculate_minimum_rows(m, d);
   double cursor_y = d->month_top_corner_y + (row_offset * d->day_height);

   int current_day = m->first_day;

   int increment = 0;


   for (int i = 0; i < d->row_count; i++) {
      for (int k = current_day; k < d->column_count; k++) {
         // When the increment reached the end of the month, end
         // the function.
         if (increment >= m->num_of_days) return 0;


         construct_day_box(cd, m->month_position, increment + 1, k);


         // Position the constructed day box on main surface
         cairo_set_source_surface (c, s, cursor_x, cursor_y);
         cairo_paint(c);

         // Move cursor one "box" over 
         cursor_x = cursor_x + d->day_width;
         increment++;
      } 
      current_day = 0;
   

   cursor_x = d->month_top_corner_x;
   cursor_y = cursor_y + d->day_height;
   }

   cairo_stroke(cd);
   return 0;
}



// Draws the month being drawn at the top of the page
int draw_month_title(cairo_t *c, struct dimensions *d, char *font_family, int font_size, char *name) {

   PangoRectangle rect;

   rect = get_logical_extents(c, font_family, font_size, name);

   //double cursor_x = (d->header_height / 2.0) - ((rect.width / 2.0));
   double cursor_x = ((d->header_width - rect.width) / 2.0);
   //double cursor_y = height + d->margin;
   double cursor_y = d->header_height - rect.height - d->margin;
   draw_text(c, cursor_x, cursor_y, font_family, font_size, name);
   return 0;
}


//int draw_weekday_names(cairo_t *c, struct dimensions *d) {
//
//}