/*
    * font.hpp
    * MontaukOS text rendering — TrueType with bitmap fallback
    * Copyright (c) 2025 Daniel Hammer
*/

#pragma once
#include "gui/gui.hpp"
#include "gui/framebuffer.hpp"
#include "gui/truetype.hpp"

namespace gui {

static constexpr int FONT_WIDTH = 8;
static constexpr int FONT_HEIGHT = 16;

// Defined by programs that ship the built-in VGA fallback. Keep the symbol
// weak so Canvas remains usable by small apps that intentionally rely only on
// TrueType fonts, while login/desktop can recover when TrueType setup fails.
extern const uint8_t font_data[256 * 16] __attribute__((weak));

// The bitmap fallback font is Code Page 437. Map a Unicode codepoint to its
// CP437 cell ('?' when it has none) so UTF-8 text still draws sensibly,
// including the box-drawing characters terminal programs use.
inline uint8_t cp437_index(uint32_t cp) {
    if (cp < 0x80) return (uint8_t)cp;
    static constexpr uint16_t high[128] = {
        0x00C7,0x00FC,0x00E9,0x00E2,0x00E4,0x00E0,0x00E5,0x00E7,
        0x00EA,0x00EB,0x00E8,0x00EF,0x00EE,0x00EC,0x00C4,0x00C5,
        0x00C9,0x00E6,0x00C6,0x00F4,0x00F6,0x00F2,0x00FB,0x00F9,
        0x00FF,0x00D6,0x00DC,0x00A2,0x00A3,0x00A5,0x20A7,0x0192,
        0x00E1,0x00ED,0x00F3,0x00FA,0x00F1,0x00D1,0x00AA,0x00BA,
        0x00BF,0x2310,0x00AC,0x00BD,0x00BC,0x00A1,0x00AB,0x00BB,
        0x2591,0x2592,0x2593,0x2502,0x2524,0x2561,0x2562,0x2556,
        0x2555,0x2563,0x2551,0x2557,0x255D,0x255C,0x255B,0x2510,
        0x2514,0x2534,0x252C,0x251C,0x2500,0x253C,0x255E,0x255F,
        0x255A,0x2554,0x2569,0x2566,0x2560,0x2550,0x256C,0x2567,
        0x2568,0x2564,0x2565,0x2559,0x2558,0x2552,0x2553,0x256B,
        0x256A,0x2518,0x250C,0x2588,0x2584,0x258C,0x2590,0x2580,
        0x03B1,0x00DF,0x0393,0x03C0,0x03A3,0x03C3,0x00B5,0x03C4,
        0x03A6,0x0398,0x03A9,0x03B4,0x221E,0x03C6,0x03B5,0x2229,
        0x2261,0x00B1,0x2265,0x2264,0x2320,0x2321,0x00F7,0x2248,
        0x00B0,0x2219,0x00B7,0x221A,0x207F,0x00B2,0x25A0,0x00A0,
    };
    for (int i = 0; i < 128; i++)
        if (high[i] == cp) return (uint8_t)(0x80 + i);
    return '?';
}

// Dynamic font height: TTF line height or 16 (bitmap fallback)
inline int system_font_height() {
    if (fonts::system_font && fonts::system_font->valid)
        return fonts::system_font->get_line_height(fonts::UI_SIZE);
    return FONT_HEIGHT;
}

// Dynamic mono font cell dimensions
inline int mono_cell_width() {
    if (fonts::mono && fonts::mono->valid) {
        // Monospace: all glyphs have the same advance
        GlyphCache* gc = fonts::mono->get_cache(fonts::TERM_SIZE);
        CachedGlyph* g = fonts::mono->get_glyph(gc, 'M');
        if (g) return g->advance;
    }
    return FONT_WIDTH;
}

inline int mono_cell_height() {
    if (fonts::mono && fonts::mono->valid)
        return fonts::mono->get_line_height(fonts::TERM_SIZE);
    return FONT_HEIGHT;
}

inline void draw_char(Framebuffer& fb, int x, int y, char c, Color fg) {
    const uint8_t* glyph = &font_data[(unsigned char)c * FONT_HEIGHT];
    for (int row = 0; row < FONT_HEIGHT; row++) {
        uint8_t bits = glyph[row];
        for (int col = 0; col < FONT_WIDTH; col++) {
            if (bits & (0x80 >> col)) {
                fb.put_pixel(x + col, y + row, fg);
            }
        }
    }
}

inline void draw_char_bg(Framebuffer& fb, int x, int y, char c, Color fg, Color bg) {
    const uint8_t* glyph = &font_data[(unsigned char)c * FONT_HEIGHT];
    for (int row = 0; row < FONT_HEIGHT; row++) {
        uint8_t bits = glyph[row];
        for (int col = 0; col < FONT_WIDTH; col++) {
            if (bits & (0x80 >> col)) {
                fb.put_pixel(x + col, y + row, fg);
            } else {
                fb.put_pixel(x + col, y + row, bg);
            }
        }
    }
}

inline void draw_text(Framebuffer& fb, int x, int y, const char* text, Color fg) {
    if (fonts::system_font && fonts::system_font->valid) {
        fonts::system_font->draw(fb, x, y, text, fg, fonts::UI_SIZE);
        return;
    }
    for (const char* p = text; *p; x += FONT_WIDTH) {
        draw_char(fb, x, y, (char)cp437_index(montauk::utf8::next(&p)), fg);
    }
}

inline void draw_text_bg(Framebuffer& fb, int x, int y, const char* text, Color fg, Color bg) {
    if (fonts::system_font && fonts::system_font->valid) {
        fonts::system_font->draw_bg(fb, x, y, text, fg, bg, fonts::UI_SIZE);
        return;
    }
    for (const char* p = text; *p; x += FONT_WIDTH) {
        draw_char_bg(fb, x, y, (char)cp437_index(montauk::utf8::next(&p)), fg, bg);
    }
}

// Width of the first `len` bytes of a UTF-8 string in the UI font.
inline int text_width_n(const char* text, int len) {
    if (fonts::system_font && fonts::system_font->valid)
        return fonts::system_font->measure_text_n(text, len, fonts::UI_SIZE);
    return montauk::utf8::count(text, len) * FONT_WIDTH;
}

inline int text_width(const char* text) {
    if (fonts::system_font && fonts::system_font->valid) {
        return fonts::system_font->measure_text(text, fonts::UI_SIZE);
    }
    return montauk::utf8::count(text) * FONT_WIDTH;
}

} // namespace gui