import os
import boto3

# Cache: built once per warm session (shared base only)
_base_prompt: str | None = None


def build_system_prompt(user_context: str = '') -> str:
    """Build system prompt from S3 workspace files + optional per-user context."""
    base = _get_base_prompt()
    if user_context:
        return base + f'\n\n---\n\n## User\n{user_context}'
    return base


def _get_base_prompt() -> str:
    global _base_prompt
    if _base_prompt is not None:
        return _base_prompt

    bucket = os.environ.get('WORKSPACE_BUCKET_NAME', '') or 'agent-claw-workspace-495395224548'
    print(f'[prompt_builder] Loading from bucket: {bucket!r}')

    if not bucket:
        print('[prompt_builder] WARNING: WORKSPACE_BUCKET_NAME not set!')
        _base_prompt = 'You are a helpful personal assistant.'
        return _base_prompt

    s3 = boto3.client('s3')
    parts = []

    for fname in ['SOUL.md', 'AGENTS.md', 'IDENTITY.md', 'TOOLS.md']:
        try:
            obj = s3.get_object(Bucket=bucket, Key=fname)
            content = obj['Body'].read().decode('utf-8')
            parts.append(f'## {fname}\n{content}')
            print(f'[prompt_builder] Loaded {fname} ({len(content)} bytes)')
        except Exception as e:
            print(f'[prompt_builder] Failed to load {fname}: {e}')

    parts.append('## Runtime\nRuntime: agent-claw | host=AgentCore | model=bedrock-claude-sonnet | channel=telegram\nCurrent date/time is provided by the system. Timezone: America/Chicago.')

    _base_prompt = '\n\n---\n\n'.join(parts)
    print(f'[prompt_builder] Base prompt built: {len(_base_prompt)} chars')
    return _base_prompt


def invalidate_prompt() -> None:
    """Force rebuild of system prompt on next invocation (call after workspace write)."""
    global _base_prompt
    _base_prompt = None