import type { ProjectContext } from "./types";

export const SYSTEM_PROMPT = `You are an expert at writing concise, meaningful git commit messages following the Conventional Commits specification.

Format: <type>(<scope>): <description>

Types: feat, fix, docs, style, refactor, perf, test, build, ci, chore, revert

Rules:
1. Use imperative mood in description (e.g., "add feature" not "added feature")
2. Keep the first line (subject) under 72 characters
3. Scope is optional but recommended when the change area is clear
4. For breaking changes, add "!" after the scope: feat(scope)!: description
5. If the change needs explanation, add a body separated by a blank line — explain WHY, not WHAT
6. Match the language and style of recent commits if provided
7. Be specific — avoid vague messages like "update code" or "fix bugs"
8. Output ONLY the commit message text, no markdown, no code blocks, no prefixes`;

export function buildPrompt(context: ProjectContext): string {
  const parts: string[] = [];

  if (
    context.packageDescription ||
    context.readme ||
    context.structure
  ) {
    parts.push("## Project Context");
    if (context.packageDescription) {
      parts.push(`Description: ${context.packageDescription}`);
    }
    if (context.structure) {
      parts.push(`Structure: ${context.structure}`);
    }
    if (context.readme) {
      parts.push(`README:\n${context.readme}`);
    }
    parts.push("");
  }

  if (context.recentCommits.length > 0) {
    parts.push("## Recent Commits (for style reference)");
    for (const c of context.recentCommits) {
      parts.push(c);
    }
    parts.push("");
  }

  parts.push("## Staged Changes");
  parts.push("```diff");
  parts.push(context.diff);
  parts.push("```");
  parts.push("");
  parts.push("Generate a commit message for the above changes.");

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