import type { ClaudeCommand, ClaudeSkill } from "./types.js";

/**
 * Build the system-prompt sections describing currently loaded commands,
 * skills, and any collisions. Returns an empty string when there is
 * nothing relevant to inject.
 */
export function buildSystemPromptSections(
  commands: ClaudeCommand[],
  skills: ClaudeSkill[],
  collisions: Map<string, string>,
): string {
  if (commands.length === 0 && skills.length === 0 && collisions.size === 0) {
    return "";
  }

  const sections: string[] = [];

  if (commands.length > 0) {
    const commandList = commands
      .map(cmd => {
        const suffix = collisions.has(cmd.name) ? ` [CONFLICT with ${collisions.get(cmd.name)}]` : "";
        return `- \`/${cmd.name}\`: ${cmd.description}${suffix}`;
      })
      .join("\n");

    sections.push(
      "## Claude Custom Commands\n" +
      "The following Claude CLI custom commands are loaded:\n\n" +
      `${commandList}\n\n` +
      "Use `/commandname` to invoke a command (e.g. `/test`, `/xyz:test1`). " +
      "Pass arguments after the command name, e.g. `/test my arguments`. " +
      "The `$ARGUMENTS` placeholder in command files will be replaced with the provided arguments.",
    );
  }

  if (collisions.size > 0) {
    const collisionList = [...collisions.entries()]
      .map(([name, source]) => `- \`/${name}\`: already registered by ${source}`)
      .join("\n");

    sections.push(
      "## Command Name Collisions\n" +
      "The following Claude command names conflict with existing commands and were not registered:\n\n" +
      `${collisionList}\n\n` +
      "Rename the .md file or move it to a subdirectory to change the command name. " +
      'For example, rename "test.md" to "mytest.md" to get `/mytest` instead of `/test`.',
    );
  }

  if (skills.length > 0) {
    const skillList = skills
      .map(s => `- \`/skill:${s.name}\`: ${s.description} (${s.dirPath})`)
      .join("\n");

    sections.push(
      "## Claude Custom Skills\n" +
      "The following skills are available as pi slash commands:\n\n" +
      `${skillList}\n\n` +
      "Use `/skill:name` to invoke a skill. " +
      "Skills are also discoverable by the agent.",
    );
  }

  return sections.join("\n\n");
}