import { join } from "node:path";
import { loadScopedConfig } from "../../src/shared/config";
import type { OutputGuardConfig, ToolGuardRule } from "./types";

export const DEFAULT_CONFIG: OutputGuardConfig = {
  enabled: true,
  defaultMaxChars: 16_000,
  defaultHeadRatio: 0.5,
  tools: {
    bash: { maxChars: 24_000, headRatio: 0.2, hint: "pipe through head/tail, add filters, or narrow the command" },
    grep: { maxChars: 16_000, headRatio: 0.8, hint: "add path/glob filters or use a more specific pattern" },
    rg: { maxChars: 16_000, headRatio: 0.8, hint: "add path/glob filters, use --max-count, or narrow the pattern" },
    read: { maxChars: 24_000, headRatio: 0.9, hint: "use offset/limit to read specific sections" },
    fd: { maxChars: 12_000, headRatio: 0.8, hint: "add --max-depth, --extension, or a more specific pattern" },
    find: { maxChars: 12_000, headRatio: 0.8, hint: "add -maxdepth, -name, or -type filters" },
  },
  exempt: [
    "web_search",
    "web_read",
    "docs_search",
    "check_search_tools",
    "verify_search_tools",
    "check_vera",
    // Subagent returns are already synthesized by the child agent
    // per its briefing; truncating defeats the round-trip cost of delegation.
    "subagent",
  ],
  notifications: {
    showTruncation: true,
  },
};

export function resolveToolRule(config: OutputGuardConfig, toolName: string): ToolGuardRule {
  const override = config.tools[toolName];
  return {
    maxChars: override?.maxChars ?? config.defaultMaxChars,
    headRatio: override?.headRatio ?? config.defaultHeadRatio,
    hint: override?.hint,
  };
}

export function loadOutputGuardConfig(cwd: string): { config: OutputGuardConfig; source: string } {
  return loadScopedConfig<Partial<OutputGuardConfig>, OutputGuardConfig>(
    cwd,
    join("config", "output-guard.json"),
    DEFAULT_CONFIG,
    (defaults, input) => {
      if (!input) return defaults;
      const tools: Record<string, Partial<ToolGuardRule>> = { ...defaults.tools };
      if (input.tools) {
        for (const [name, rule] of Object.entries(input.tools)) {
          tools[name] = { ...tools[name], ...rule };
        }
      }
      const exempt = input.exempt ?? defaults.exempt;
      return {
        enabled: input.enabled ?? defaults.enabled,
        defaultMaxChars: input.defaultMaxChars ?? defaults.defaultMaxChars,
        defaultHeadRatio: input.defaultHeadRatio ?? defaults.defaultHeadRatio,
        tools,
        exempt,
        notifications: {
          showTruncation: input.notifications?.showTruncation ?? defaults.notifications.showTruncation,
        },
      };
    },
  );
}