import type { ContextPruningToolMatch } from "./settings.js";

function normalizePatterns(patterns?: string[]): string[] {
  if (!Array.isArray(patterns)) {
    return [];
  }
  return patterns
    .map((p) =>
      String(p ?? "")
        .trim()
        .toLowerCase(),
    )
    .filter(Boolean);
}

type CompiledPattern =
  | { kind: "all" }
  | { kind: "exact"; value: string }
  | { kind: "regex"; value: RegExp };

function compilePattern(pattern: string): CompiledPattern {
  if (pattern === "*") {
    return { kind: "all" };
  }
  if (!pattern.includes("*")) {
    return { kind: "exact", value: pattern };
  }

  const escaped = pattern.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
  const re = new RegExp(`^${escaped.replaceAll("\\*", ".*")}$`);
  return { kind: "regex", value: re };
}

function compilePatterns(patterns?: string[]): CompiledPattern[] {
  return normalizePatterns(patterns).map(compilePattern);
}

function matchesAny(toolName: string, patterns: CompiledPattern[]): boolean {
  for (const p of patterns) {
    if (p.kind === "all") {
      return true;
    }
    if (p.kind === "exact" && toolName === p.value) {
      return true;
    }
    if (p.kind === "regex" && p.value.test(toolName)) {
      return true;
    }
  }
  return false;
}

export function makeToolPrunablePredicate(
  match: ContextPruningToolMatch,
): (toolName: string) => boolean {
  const deny = compilePatterns(match.deny);
  const allow = compilePatterns(match.allow);

  return (toolName: string) => {
    const normalized = toolName.trim().toLowerCase();
    if (matchesAny(normalized, deny)) {
      return false;
    }
    if (allow.length === 0) {
      return true;
    }
    return matchesAny(normalized, allow);
  };
}