/**
 * Declare parser — parses ```csv role=declare code blocks from markdown.
 *
 * Shared between CLI completions scanner and browser-side completions.
 *
 * Format:
 *   tag,key,expr
 *   ,$hp,$con*5+$mod_hp          ← variable declaration
 *   ,$ac,10+$dex                   ← variable declaration
 *   #warrior,$mod_hp,20           ← tag modifier
 *   #warrior,$mod_str,1           ← tag modifier
 *
 * When `tag` is empty: $key is a reactively computed variable.
 * When `tag` is present: when #tag is active, $key gets expr added to its base.
 */

export interface VarDeclaration {
  key: string;        // "$hp" (always starts with $)
  expression: string; // "$con*5+$mod_hp"
}

export interface TagModifier {
  tag: string;        // "#warrior"
  target: string;     // "$mod_hp"
  expression: string; // "20"
}

export interface DeclareResult {
  variables: VarDeclaration[];
  tagModifiers: TagModifier[];
}

/**
 * Parse a ```csv role=declare block.
 */
export function parseDeclareCsv(csv: string, source: string): DeclareResult {
  const lines = csv.trim().split(/\r?\n/);
  if (lines.length === 0) return { variables: [], tagModifiers: [] };

  // First line is header; validate it
  const headers = lines[0].split(",").map((h) => h.trim().toLowerCase());
  if (headers[0] !== "tag" || headers[1] !== "key" || headers[2] !== "expr") {
    throw new Error(
      `${source}: role=declare blocks must have headers "tag,key,expr". Got: ${headers.join(",")}`,
    );
  }

  const variables: VarDeclaration[] = [];
  const tagModifiers: TagModifier[] = [];

  for (let i = 1; i < lines.length; i++) {
    const row = lines[i].trim();
    if (!row || row.startsWith("#")) continue;

    const cols = splitCsvRow(row);
    if (cols.length < 3) continue;

    const tag = cols[0]?.trim() ?? "";
    const key = cols[1]?.trim() ?? "";
    const expr = cols[2]?.trim() ?? "";

    if (!key || !expr) {
      console.warn(`${source}:${i + 1}: skipping row with empty key or expr`);
      continue;
    }

    if (tag) {
      // Tag modifier
      if (!tag.startsWith("#")) {
        throw new Error(
          `${source}:${i + 1}: tag must start with #, got "${tag}"`,
        );
      }
      if (!key.startsWith("$")) {
        throw new Error(
          `${source}:${i + 1}: key must start with $, got "${key}"`,
        );
      }
      tagModifiers.push({ tag, target: key, expression: expr });
    } else {
      // Variable declaration
      if (!key.startsWith("$")) {
        throw new Error(
          `${source}:${i + 1}: key must start with $, got "${key}"`,
        );
      }
      variables.push({ key, expression: expr });
    }
  }

  return { variables, tagModifiers };
}

// ---------------------------------------------------------------------------
// CSV row splitter
// ---------------------------------------------------------------------------

function splitCsvRow(row: string): string[] {
  const cols: string[] = [];
  let current = "";
  let inQuote = false;

  for (let i = 0; i < row.length; i++) {
    const ch = row[i];
    if (ch === '"') {
      inQuote = !inQuote;
    } else if (ch === "," && !inQuote) {
      cols.push(current);
      current = "";
    } else {
      current += ch;
    }
  }
  cols.push(current);
  return cols;
}