import difflib
from typing import Dict, List, Optional, Tuple

from .colors import Colors


class DiffStats:
    def __init__(self):
        self.insertions = 0
        self.deletions = 0
        self.modifications = 0
        self.files_changed = 0

    @property
    def total_changes(self):
        return self.insertions + self.deletions

    def __str__(self):
        return f"{self.files_changed} file(s) changed, {self.insertions} insertions(+), {self.deletions} deletions(-)"


class DiffLine:
    def __init__(
        self,
        line_type: str,
        content: str,
        old_line_num: Optional[int] = None,
        new_line_num: Optional[int] = None,
    ):
        self.line_type = line_type
        self.content = content
        self.old_line_num = old_line_num
        self.new_line_num = new_line_num

    def format(self, show_line_nums: bool = True) -> str:
        color = {
            "add": Colors.GREEN,
            "delete": Colors.RED,
            "context": Colors.GRAY,
            "header": Colors.CYAN,
            "stats": Colors.BLUE,
        }.get(self.line_type, Colors.RESET)

        prefix = {
            "add": "+ ",
            "delete": "- ",
            "context": "  ",
            "header": "",
            "stats": "",
        }.get(self.line_type, "  ")

        if show_line_nums and self.line_type in ("add", "delete", "context"):
            old_num = str(self.old_line_num) if self.old_line_num else " "
            new_num = str(self.new_line_num) if self.new_line_num else " "
            line_num_str = f"{Colors.YELLOW}{old_num:>4} {new_num:>4}{Colors.RESET} "
        else:
            line_num_str = ""

        return f"{line_num_str}{color}{prefix}{self.content}{Colors.RESET}"


class DiffDisplay:
    def __init__(self, context_lines: int = 3):
        self.context_lines = context_lines

    def create_diff(
        self, old_content: str, new_content: str, filename: str = "file"
    ) -> Tuple[List[DiffLine], DiffStats]:
        old_lines = old_content.splitlines(keepends=True)
        new_lines = new_content.splitlines(keepends=True)

        diff_lines = []
        stats = DiffStats()
        stats.files_changed = 1

        diff = difflib.unified_diff(
            old_lines,
            new_lines,
            fromfile=f"a/{filename}",
            tofile=f"b/{filename}",
            n=self.context_lines,
        )

        old_line_num = 0
        new_line_num = 0

        for line in diff:
            if line.startswith("---") or line.startswith("+++"):
                diff_lines.append(DiffLine("header", line.rstrip()))
            elif line.startswith("@@"):
                diff_lines.append(DiffLine("header", line.rstrip()))
                old_line_num, new_line_num = self._parse_hunk_header(line)
            elif line.startswith("+"):
                stats.insertions += 1
                diff_lines.append(DiffLine("add", line[1:].rstrip(), None, new_line_num))
                new_line_num += 1
            elif line.startswith("-"):
                stats.deletions += 1
                diff_lines.append(DiffLine("delete", line[1:].rstrip(), old_line_num, None))
                old_line_num += 1
            elif line.startswith(" "):
                diff_lines.append(
                    DiffLine("context", line[1:].rstrip(), old_line_num, new_line_num)
                )
                old_line_num += 1
                new_line_num += 1

        stats.modifications = min(stats.insertions, stats.deletions)

        return diff_lines, stats

    def _parse_hunk_header(self, header: str) -> Tuple[int, int]:
        try:
            parts = header.split("@@")[1].strip().split()
            old_start = int(parts[0].split(",")[0].replace("-", ""))
            new_start = int(parts[1].split(",")[0].replace("+", ""))
            return old_start, new_start
        except (IndexError, ValueError):
            return 0, 0

    def render_diff(
        self,
        diff_lines: List[DiffLine],
        stats: DiffStats,
        show_line_nums: bool = True,
        show_stats: bool = True,
    ) -> str:
        output = []

        if show_stats:
            output.append(f"\n{Colors.BOLD}{Colors.BLUE}{'=' * 60}{Colors.RESET}")
            output.append(f"{Colors.BOLD}{Colors.BLUE}DIFF SUMMARY{Colors.RESET}")
            output.append(f"{Colors.BOLD}{Colors.BLUE}{'=' * 60}{Colors.RESET}")
            output.append(f"{Colors.BLUE}{stats}{Colors.RESET}\n")

        for line in diff_lines:
            output.append(line.format(show_line_nums))

        if show_stats:
            output.append(f"\n{Colors.BOLD}{Colors.BLUE}{'=' * 60}{Colors.RESET}\n")

        return "\n".join(output)

    def display_file_diff(
        self,
        old_content: str,
        new_content: str,
        filename: str = "file",
        show_line_nums: bool = True,
    ) -> str:
        diff_lines, stats = self.create_diff(old_content, new_content, filename)

        if not diff_lines:
            return f"{Colors.GRAY}No changes detected{Colors.RESET}"

        return self.render_diff(diff_lines, stats, show_line_nums)

    def display_side_by_side(
        self,
        old_content: str,
        new_content: str,
        filename: str = "file",
        width: int = 80,
    ) -> str:
        old_lines = old_content.splitlines()
        new_lines = new_content.splitlines()

        matcher = difflib.SequenceMatcher(None, old_lines, new_lines)
        output = []

        output.append(f"\n{Colors.BOLD}{Colors.BLUE}{'=' * width}{Colors.RESET}")
        output.append(
            f"{Colors.BOLD}{Colors.BLUE}SIDE-BY-SIDE COMPARISON: {filename}{Colors.RESET}"
        )
        output.append(f"{Colors.BOLD}{Colors.BLUE}{'=' * width}{Colors.RESET}\n")

        half_width = (width - 5) // 2

        for tag, i1, i2, j1, j2 in matcher.get_opcodes():
            if tag == "equal":
                for i, (old_line, new_line) in enumerate(zip(old_lines[i1:i2], new_lines[j1:j2])):
                    old_display = old_line[:half_width].ljust(half_width)
                    new_display = new_line[:half_width].ljust(half_width)
                    output.append(f"{Colors.GRAY}{old_display} | {new_display}{Colors.RESET}")
            elif tag == "replace":
                max_lines = max(i2 - i1, j2 - j1)
                for i in range(max_lines):
                    old_line = old_lines[i1 + i] if i1 + i < i2 else ""
                    new_line = new_lines[j1 + i] if j1 + i < j2 else ""
                    old_display = old_line[:half_width].ljust(half_width)
                    new_display = new_line[:half_width].ljust(half_width)
                    output.append(
                        f"{Colors.RED}{old_display}{Colors.RESET} | {Colors.GREEN}{new_display}{Colors.RESET}"
                    )
            elif tag == "delete":
                for old_line in old_lines[i1:i2]:
                    old_display = old_line[:half_width].ljust(half_width)
                    output.append(f"{Colors.RED}{old_display} | {' ' * half_width}{Colors.RESET}")
            elif tag == "insert":
                for new_line in new_lines[j1:j2]:
                    new_display = new_line[:half_width].ljust(half_width)
                    output.append(f"{' ' * half_width} | {Colors.GREEN}{new_display}{Colors.RESET}")

        output.append(f"\n{Colors.BOLD}{Colors.BLUE}{'=' * width}{Colors.RESET}\n")
        return "\n".join(output)


def display_diff(
    old_content: str,
    new_content: str,
    filename: str = "file",
    format_type: str = "unified",
    context_lines: int = 3,
) -> str:
    displayer = DiffDisplay(context_lines)

    if format_type == "side-by-side":
        return displayer.display_side_by_side(old_content, new_content, filename)
    else:
        return displayer.display_file_diff(old_content, new_content, filename)


def get_diff_stats(old_content: str, new_content: str) -> Dict[str, int]:
    displayer = DiffDisplay()
    _, stats = displayer.create_diff(old_content, new_content)

    return {
        "insertions": stats.insertions,
        "deletions": stats.deletions,
        "modifications": stats.modifications,
        "total_changes": stats.total_changes,
        "files_changed": stats.files_changed,
    }