#include <gtk/gtk.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// Widgets we need to access globally
static GtkWidget *entry_x;
static GtkWidget *text_coeffs;
static GtkWidget *label_result;

static void calculate(GtkWidget *widget, gpointer data) {
    (void)widget; (void)data;

    // Read x
    const char *x_str = gtk_entry_get_text(GTK_ENTRY(entry_x));
    double x;
    if (sscanf(x_str, "%lf", &x) != 1) {
        gtk_label_set_text(GTK_LABEL(label_result), "Chyba: Nepodarilo sa nacitat zaklad x");
        return;
    }

    // Read coefficients from text view
    GtkTextBuffer *buf = gtk_text_view_get_buffer(GTK_TEXT_VIEW(text_coeffs));
    GtkTextIter start, end;
    gtk_text_buffer_get_start_iter(buf, &start);
    gtk_text_buffer_get_end_iter(buf, &end);
    char *text = gtk_text_buffer_get_text(buf, &start, &end, FALSE);

    double coeffs[256];
    int n = 0;
    char *line = strtok(text, "\n");
    while (line != NULL && n < 256) {
        // skip empty lines
        if (strlen(line) == 0 || line[0] == '\r') {
            line = strtok(NULL, "\n");
            continue;
        }
        if (sscanf(line, "%lf", &coeffs[n]) != 1) {
            char msg[128];
            snprintf(msg, sizeof(msg), "Chyba: Nepodarilo sa nacitat polynom na %d mieste.", n + 1);
            gtk_label_set_text(GTK_LABEL(label_result), msg);
            g_free(text);
            return;
        }
        n++;
        line = strtok(NULL, "\n");
    }
    g_free(text);

    if (n == 0) {
        gtk_label_set_text(GTK_LABEL(label_result), "Chyba: Nepodarilo sa nacitat polynom na 2 mieste.");
        return;
    }

    // Horner's method
    double result = 0.0;
    for (int i = 0; i < n; i++) {
        result = result * x + coeffs[i];
    }

    char msg[128];
    snprintf(msg, sizeof(msg), "Vysledok je: %.2f", result);
    gtk_label_set_text(GTK_LABEL(label_result), msg);
}

static void activate(GtkApplication *app, gpointer user_data) {
    (void)user_data;

    GtkWidget *window = gtk_application_window_new(app);
    gtk_window_set_title(GTK_WINDOW(window), "Polynóm kalkulačka");
    gtk_window_set_default_size(GTK_WINDOW(window), 350, 450);
    gtk_container_set_border_width(GTK_CONTAINER(window), 16);

    GtkWidget *box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 10);
    gtk_container_add(GTK_CONTAINER(window), box);

    // X input
    GtkWidget *lbl_x = gtk_label_new("Hodnota x:");
    gtk_widget_set_halign(lbl_x, GTK_ALIGN_START);
    gtk_box_pack_start(GTK_BOX(box), lbl_x, FALSE, FALSE, 0);

    entry_x = gtk_entry_new();
    gtk_entry_set_placeholder_text(GTK_ENTRY(entry_x), "napr. 4 alebo 2.5");
    gtk_box_pack_start(GTK_BOX(box), entry_x, FALSE, FALSE, 0);

    // Coefficients input
    GtkWidget *lbl_c = gtk_label_new("Koeficienty (každý na novom riadku, od najvyššieho rádu):");
    gtk_widget_set_halign(lbl_c, GTK_ALIGN_START);
    gtk_label_set_line_wrap(GTK_LABEL(lbl_c), TRUE);
    gtk_box_pack_start(GTK_BOX(box), lbl_c, FALSE, FALSE, 0);

    GtkWidget *scroll = gtk_scrolled_window_new(NULL, NULL);
    gtk_scrolled_window_set_min_content_height(GTK_SCROLLED_WINDOW(scroll), 150);
    gtk_box_pack_start(GTK_BOX(box), scroll, TRUE, TRUE, 0);

    text_coeffs = gtk_text_view_new();
    gtk_text_view_set_monospace(GTK_TEXT_VIEW(text_coeffs), TRUE);
    gtk_container_add(GTK_CONTAINER(scroll), text_coeffs);

    // Calculate button
    GtkWidget *btn = gtk_button_new_with_label("Vypočítať");
    g_signal_connect(btn, "clicked", G_CALLBACK(calculate), NULL);
    gtk_box_pack_start(GTK_BOX(box), btn, FALSE, FALSE, 0);

    // Result label
    label_result = gtk_label_new("Vysledok sa zobrazí tu.");
    gtk_widget_set_halign(label_result, GTK_ALIGN_START);
    gtk_label_set_selectable(GTK_LABEL(label_result), TRUE);

    // Style the result label
    GtkStyleContext *ctx = gtk_widget_get_style_context(label_result);
    GtkCssProvider *provider = gtk_css_provider_new();
    gtk_css_provider_load_from_data(provider, "label { font-size: 16px; font-weight: bold; }", -1, NULL);
    gtk_style_context_add_provider(ctx, GTK_STYLE_PROVIDER(provider), GTK_STYLE_PROVIDER_PRIORITY_USER);

    gtk_box_pack_start(GTK_BOX(box), label_result, FALSE, FALSE, 0);

    gtk_widget_show_all(window);
}

int main(int argc, char **argv) {
    GtkApplication *app = gtk_application_new("sk.tuke.pvjc.polynom", G_APPLICATION_DEFAULT_FLAGS);
    g_signal_connect(app, "activate", G_CALLBACK(activate), NULL);
    int status = g_application_run(G_APPLICATION(app), argc, argv);
    g_object_unref(app);
    return status;
}