#include "MarkdownHighlighter.h"
#include "Buffer.h"
#include <cctype>

namespace kte {

static void push_span(std::vector<HighlightSpan> &out, int a, int b, TokenKind k) {
    if (b > a) out.push_back({a,b,k});
}

void MarkdownHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
{
    LineState st; // not used in stateless entry
    (void)HighlightLineStateful(buf, row, st, out);
}

StatefulHighlighter::LineState MarkdownHighlighter::HighlightLineStateful(const Buffer &buf, int row, const LineState &prev, std::vector<HighlightSpan> &out) const
{
    StatefulHighlighter::LineState state = prev;
    const auto &rows = buf.Rows();
    if (row < 0 || static_cast<std::size_t>(row) >= rows.size()) return state;
    std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
    int n = static_cast<int>(s.size());

    // Reuse in_block_comment flag as "in fenced code" state.
    if (state.in_block_comment) {
        // If line contains closing fence ``` then close after it
        auto pos = s.find("```");
        if (pos == std::string::npos) {
            push_span(out, 0, n, TokenKind::String);
            state.in_block_comment = true;
            return state;
        } else {
            int end = static_cast<int>(pos + 3);
            push_span(out, 0, end, TokenKind::String);
            // rest of line processed normally after fence
            int i = end;
            // whitespace
            if (i < n) push_span(out, i, n, TokenKind::Default);
            state.in_block_comment = false;
            return state;
        }
    }

    // Detect fenced code block start at beginning (allow leading spaces)
    int bol = 0; while (bol < n && (s[bol]==' '||s[bol]=='\t')) ++bol;
    if (bol + 3 <= n && s.compare(bol, 3, "```") == 0) {
        push_span(out, bol, n, TokenKind::String);
        state.in_block_comment = true; // enter fenced mode
        return state;
    }

    // Headings: lines starting with 1-6 '#'
    if (bol < n && s[bol] == '#') {
        int j = bol; while (j < n && s[j] == '#') ++j; // hashes
        // include following space and text as Keyword to stand out
        push_span(out, bol, n, TokenKind::Keyword);
        return state;
    }

    // Process inline: emphasis and code spans
    int i = 0;
    while (i < n) {
        char c = s[i];
        if (c == '`') {
            int j = i + 1; while (j < n && s[j] != '`') ++j; if (j < n) ++j;
            push_span(out, i, j, TokenKind::String); i = j; continue;
        }
        if (c == '*' || c == '_') {
            // bold/italic markers: treat the marker and until next same marker as Type to highlight
            char m = c; int j = i + 1; while (j < n && s[j] != m) ++j; if (j < n) ++j;
            push_span(out, i, j, TokenKind::Type); i = j; continue;
        }
        // links []() minimal: treat [text](url) as Function
        if (c == '[') {
            int j = i + 1; while (j < n && s[j] != ']') ++j; if (j < n) ++j; // include ]
            if (j < n && s[j] == '(') { while (j < n && s[j] != ')') ++j; if (j < n) ++j; }
            push_span(out, i, j, TokenKind::Function); i = j; continue;
        }
        // whitespace
        if (c == ' ' || c == '\t') { int j=i+1; while (j<n && (s[j]==' '||s[j]=='\t')) ++j; push_span(out, i, j, TokenKind::Whitespace); i=j; continue; }
        // fallback: default single char
        push_span(out, i, i+1, TokenKind::Default); ++i;
    }
    return state;
}

} // namespace kte