"""Tests for SystemPrompter."""

import sys
from pathlib import Path

sys.path.insert(0, str(Path(__file__).parent.parent))

import pytest
from backend.managers.system_prompter import SystemPrompter, MAX_FILE_CHARS  # MAX_FILE_CHARS: character limit before content is truncated


class TestSystemPrompterBasePrompt:
    """Tests for generate_prompt() without file context."""

    def test_returns_non_empty_string(self):
        prompt = SystemPrompter.generate_prompt()
        assert isinstance(prompt, str)
        assert len(prompt) > 0

    def test_describes_code_assistant(self):
        prompt = SystemPrompter.generate_prompt()
        assert "code assistant" in prompt.lower()

    def test_contains_no_file_xml_tag(self):
        prompt = SystemPrompter.generate_prompt()
        assert "<file" not in prompt
        assert "<code>" not in prompt

    def test_none_equals_no_argument(self):
        assert SystemPrompter.generate_prompt(file_context=None) == SystemPrompter.generate_prompt()

    def test_empty_dict_behaves_like_none(self):
        # {} is falsy in Python, so the implementation treats it the same as None (no file context).
        assert SystemPrompter.generate_prompt(file_context={}) == SystemPrompter.generate_prompt()


class TestSystemPrompterWithFileContext:
    """Tests for generate_prompt() with file_context provided."""

    def test_includes_filename(self):
        prompt = SystemPrompter.generate_prompt(file_context={"name": "main.py", "content": ""})
        assert "main.py" in prompt

    def test_includes_file_content(self):
        prompt = SystemPrompter.generate_prompt(file_context={"name": "app.py", "content": "x = 42"})
        assert "x = 42" in prompt

    def test_uses_xml_file_tag(self):
        prompt = SystemPrompter.generate_prompt(file_context={"name": "f.py", "content": "pass"})
        assert "<file" in prompt

    def test_uses_xml_code_tag(self):
        prompt = SystemPrompter.generate_prompt(file_context={"name": "f.py", "content": "pass"})
        assert "<code>" in prompt

    def test_with_context_is_longer_than_base(self):
        base = SystemPrompter.generate_prompt()
        with_ctx = SystemPrompter.generate_prompt(file_context={"name": "f.py", "content": "x=1"})
        assert len(with_ctx) > len(base)

    def test_missing_name_key_uses_unknown(self):
        prompt = SystemPrompter.generate_prompt(file_context={"content": "some code"})
        assert "unknown" in prompt

    def test_missing_content_key_does_not_raise(self):
        prompt = SystemPrompter.generate_prompt(file_context={"name": "empty.py"})
        assert "empty.py" in prompt


class TestSystemPrompterTruncation:
    """Tests for file content truncation."""

    def test_large_file_is_truncated(self):
        large = "a" * (MAX_FILE_CHARS + 500)
        prompt = SystemPrompter.generate_prompt(file_context={"name": "big.py", "content": large})
        assert "[truncated]" in prompt

    def test_small_file_is_not_truncated(self):
        content = "print('hello')"
        prompt = SystemPrompter.generate_prompt(file_context={"name": "small.py", "content": content})
        assert "[truncated]" not in prompt
        assert content in prompt

    def test_file_exactly_at_limit_is_not_truncated(self):
        content = "x" * MAX_FILE_CHARS
        prompt = SystemPrompter.generate_prompt(file_context={"name": "f.py", "content": content})
        assert "[truncated]" not in prompt

    def test_file_one_over_limit_is_truncated(self):
        content = "x" * (MAX_FILE_CHARS + 1)
        prompt = SystemPrompter.generate_prompt(file_context={"name": "f.py", "content": content})
        assert "[truncated]" in prompt


class TestSystemPrompterSpecialCharacters:
    """Tests that XML special characters in file content are handled without breaking the prompt."""

    def test_less_than_in_content_does_not_break_prompt(self):
        prompt = SystemPrompter.generate_prompt(
            file_context={"name": "f.py", "content": "if x < 10:"}
        )
        assert "if x < 10:" in prompt

    def test_greater_than_in_content_does_not_break_prompt(self):
        prompt = SystemPrompter.generate_prompt(
            file_context={"name": "f.py", "content": "if x > 0:"}
        )
        assert "if x > 0:" in prompt

    def test_ampersand_in_content_does_not_break_prompt(self):
        prompt = SystemPrompter.generate_prompt(
            file_context={"name": "f.py", "content": "# true & false"}
        )
        assert "true & false" in prompt

    def test_xml_tags_in_content_are_preserved_literally(self):
        # User code often contains HTML or XML. The prompt builder must embed it
        # verbatim — escaping or stripping tags would corrupt the file content.
        prompt = SystemPrompter.generate_prompt(
            file_context={"name": "template.html", "content": "<div>hello</div>"}
        )
        assert "<div>hello</div>" in prompt

    def test_prompt_still_contains_file_xml_tag_with_special_content(self):
        # Verifies that special characters in the content don't corrupt the surrounding
        # structural tags (<file ...> and <code>) that the LLM relies on for context.
        prompt = SystemPrompter.generate_prompt(
            file_context={"name": "f.py", "content": "x < y and a > b"}
        )
        assert "<file" in prompt
        assert "<code>" in prompt