'use strict';

function ins_plugin(md) {
  // Insert each marker as a separate text token, and add it to delimiter list
  //
  function tokenize(state, silent) {
    const start = state.pos;
    const marker = state.src.charCodeAt(start);
    if (silent) {
      return false;
    }
    if (marker !== 0x3D /* = */) {
      return false;
    }
    const scanned = state.scanDelims(state.pos, true);
    let len = scanned.length;
    const ch = String.fromCharCode(marker);
    if (len < 2) {
      return false;
    }
    if (len % 2) {
      const token = state.push('text', '', 0);
      token.content = ch;
      len--;
    }
    for (let i = 0; i < len; i += 2) {
      const token = state.push('text', '', 0);
      token.content = ch + ch;
      if (!scanned.can_open && !scanned.can_close) {
        continue;
      }
      state.delimiters.push({
        marker,
        length: 0,
        // disable "rule of 3" length checks meant for emphasis
        jump: i / 2,
        // 1 delimiter = 2 characters
        token: state.tokens.length - 1,
        end: -1,
        open: scanned.can_open,
        close: scanned.can_close
      });
    }
    state.pos += scanned.length;
    return true;
  }

  // Walk through delimiter list and replace text tokens with tags
  //
  function postProcess(state, delimiters) {
    const loneMarkers = [];
    const max = delimiters.length;
    for (let i = 0; i < max; i++) {
      const startDelim = delimiters[i];
      if (startDelim.marker !== 0x3D /* = */) {
        continue;
      }
      if (startDelim.end === -1) {
        continue;
      }
      const endDelim = delimiters[startDelim.end];
      const token_o = state.tokens[startDelim.token];
      token_o.type = 'mark_open';
      token_o.tag = 'mark';
      token_o.nesting = 1;
      token_o.markup = '==';
      token_o.content = '';
      const token_c = state.tokens[endDelim.token];
      token_c.type = 'mark_close';
      token_c.tag = 'mark';
      token_c.nesting = -1;
      token_c.markup = '==';
      token_c.content = '';
      if (state.tokens[endDelim.token - 1].type === 'text' && state.tokens[endDelim.token - 1].content === '=') {
        loneMarkers.push(endDelim.token - 1);
      }
    }

    // If a marker sequence has an odd number of characters, it's splitted
    // like this: `~~~~~` -> `~` + `~~` + `~~`, leaving one marker at the
    // start of the sequence.
    //
    // So, we have to move all those markers after subsequent s_close tags.
    //
    while (loneMarkers.length) {
      const i = loneMarkers.pop();
      let j = i + 1;
      while (j < state.tokens.length && state.tokens[j].type === 'mark_close') {
        j++;
      }
      j--;
      if (i !== j) {
        const token = state.tokens[j];
        state.tokens[j] = state.tokens[i];
        state.tokens[i] = token;
      }
    }
  }
  md.inline.ruler.before('emphasis', 'mark', tokenize);
  md.inline.ruler2.before('emphasis', 'mark', function (state) {
    let curr;
    const tokens_meta = state.tokens_meta;
    const max = (state.tokens_meta || []).length;
    postProcess(state, state.delimiters);
    for (curr = 0; curr < max; curr++) {
      if (tokens_meta[curr] && tokens_meta[curr].delimiters) {
        postProcess(state, tokens_meta[curr].delimiters);
      }
    }
  });
}

module.exports = ins_plugin;
