#include "gemtext.h"

#include <cstdint>

namespace roro::gemini {

namespace {
std::string trim(const std::string& s) {
    size_t a = s.find_first_not_of(" \t"), b = s.find_last_not_of(" \t");
    return a == std::string::npos ? "" : s.substr(a, b - a + 1);
}
}  // namespace

GemLine parseGemLine(const std::string& line, bool& pre) {
    GemLine g;
    if (line.compare(0, 3, "```") == 0) {
        g.type = LineType::PreToggle;
        g.text = trim(line.substr(3));
        pre = !pre;
    } else if (pre) {
        g.type = LineType::Preformatted;
        g.text = line;
    } else if (line.compare(0, 2, "=>") == 0) {
        g.type = LineType::Link;
        std::string rest = trim(line.substr(2));
        size_t gap = rest.find_first_of(" \t");
        g.url = rest.substr(0, gap);
        g.text = gap == std::string::npos ? "" : trim(rest.substr(gap));
        if (g.text.empty()) g.text = g.url;
    } else if (line.compare(0, 3, "###") == 0) {
        g.type = LineType::Heading3;
        g.text = trim(line.substr(3));
    } else if (line.compare(0, 2, "##") == 0) {
        g.type = LineType::Heading2;
        g.text = trim(line.substr(2));
    } else if (line.compare(0, 1, "#") == 0) {
        g.type = LineType::Heading1;
        g.text = trim(line.substr(1));
    } else if (line.compare(0, 2, "* ") == 0) {
        g.type = LineType::ListItem;
        g.text = trim(line.substr(2));
    } else if (line.compare(0, 1, ">") == 0) {
        g.type = LineType::Quote;
        g.text = trim(line.substr(1));
    } else {
        g.text = line;
    }
    return g;
}

std::vector<GemLine> parseGemtext(const std::string& document) {
    std::vector<GemLine> lines;
    bool pre = false;
    size_t start = 0;
    while (start < document.size()) {
        size_t end = document.find('\n', start);
        if (end == std::string::npos) end = document.size();
        std::string line = document.substr(start, end - start);
        if (!line.empty() && line.back() == '\r') line.pop_back();
        start = end + 1;
        lines.push_back(parseGemLine(line, pre));
    }
    return lines;
}

std::string displayText(const std::string& s) {
    std::string out;
    size_t column = 0;
    for (size_t i = 0; i < s.size();) {
        unsigned char c = static_cast<unsigned char>(s[i]);
        if (c == '\t') {
            do out += ' ';
            while (++column % 4);
            i++;
            continue;
        }
        if (c < 0x80) {
            out += static_cast<char>(c);
            i++;
        } else {
            int len = (c & 0xE0) == 0xC0 ? 2 : (c & 0xF0) == 0xE0 ? 3 : (c & 0xF8) == 0xF0 ? 4 : 0;
            bool valid = len > 0 && i + len <= s.size();
            for (int k = 1; valid && k < len; k++) valid = (static_cast<unsigned char>(s[i + k]) & 0xC0) == 0x80;
            if (!valid) {
                out += '?';
                i++;
            } else {
                uint32_t cp = len == 2 ? (c & 0x1F) : len == 3 ? (c & 0x0F) : (c & 0x07);
                for (int k = 1; k < len; k++) cp = (cp << 6) | (static_cast<unsigned char>(s[i + k]) & 0x3F);
                if (cp <= 0xFF) out.append(s, i, len);  // Latin-1: the fonts have it
                else out += '?';
                i += len;
            }
        }
        column++;
    }
    return out;
}

}  // namespace roro::gemini