"""AST-based code dependency graph for structured code analysis."""

import ast
import re
from dataclasses import dataclass, field
from pathlib import Path


@dataclass
class CodeNode:
    """A node in the code graph — file, function, class, or import."""

    id: str
    kind: str
    name: str
    file: str
    line: int
    metadata: dict = field(default_factory=dict)


@dataclass
class CodeEdge:
    """A directed edge — call, import, containment, or inheritance."""

    source: str
    target: str
    kind: str


_SOURCE_EXTENSIONS = {".py", ".js", ".ts", ".jsx", ".tsx", ".java", ".go", ".rb"}


class CodeGraph:
    """Lightweight code dependency graph built from AST and regex analysis."""

    def __init__(self) -> None:
        self.nodes: dict[str, CodeNode] = {}
        self.edges: list[CodeEdge] = []
        self._file_contents: dict[str, list[str]] = {}

    def build_from_directory(self, target_dir: str) -> None:
        """Scan all source files in *target_dir* and populate the graph."""
        root = Path(target_dir)
        for p in sorted(root.rglob("*")):
            if p.suffix in _SOURCE_EXTENSIONS and p.is_file():
                self.build_from_file(str(p), str(root))

    def build_from_file(self, filepath: str, root: str = "") -> None:
        """Parse a single file and add its nodes/edges."""
        path = Path(filepath)
        rel = path.relative_to(root) if root else path.name
        ext = path.suffix

        try:
            source = path.read_text(errors="replace")
        except OSError:
            return

        self._file_contents[str(rel)] = source.splitlines()

        file_id = str(rel)
        self.nodes[file_id] = CodeNode(
            id=file_id, kind="file", name=path.name, file=str(rel), line=0,
        )

        if ext == ".py":
            self._parse_python(source, str(rel), file_id)
        elif ext in {".js", ".ts", ".jsx", ".tsx"}:
            self._parse_javascript(source, str(rel), file_id)

    def get_file_summary(self, filepath: str) -> str:
        """Return a compact summary of what a file contains."""
        lines: list[str] = []
        for node in sorted(
            (n for n in self.nodes.values() if n.file == filepath and n.kind != "file"),
            key=lambda n: n.line,
        ):
            lines.append(f"L{node.line}: [{node.kind}] {node.name}")
        if not lines:
            return f"No structured elements found in {filepath}"
        return f"=== {filepath} ===\n" + "\n".join(lines)

    def get_function_source(self, filepath: str, function_name: str) -> str:
        """Return the source lines of a function."""
        raw_lines = self._file_contents.get(filepath, [])
        if not raw_lines:
            return f"File {filepath} not cached."

        for node in self.nodes.values():
            if node.file == filepath and node.name == function_name and node.kind == "function":
                start = node.line - 1
                collected: list[str] = []
                for i in range(start, len(raw_lines)):
                    if i > start and raw_lines[i].strip() and not raw_lines[i].startswith((" ", "\t")):
                        break
                    collected.append(f"{i+1}: {raw_lines[i]}")
                return "\n".join(collected) if collected else "Function body not available."

        return f"Function '{function_name}' not found in {filepath}."

    def trace_calls(self, function_name: str, depth: int = 3) -> str:
        """Trace the call chain from *function_name* up to *depth* hops."""
        chains: list[list[str]] = []
        self._trace_recursive(function_name, depth, [function_name], chains)
        if not chains:
            return f"No call chain found for '{function_name}'."
        lines: list[str] = []
        for chain in chains:
            lines.append(" → ".join(chain))
        return "\n".join(lines)

    def get_callers(self, function_name: str) -> list[str]:
        """Return all functions that call *function_name*."""
        callers: list[str] = []
        for edge in self.edges:
            if edge.kind == "calls" and edge.target.endswith(f":{function_name}"):
                callers.append(edge.source)
        return callers

    def get_imports(self, filepath: str) -> list[str]:
        """Return all imports in a file."""
        imports: list[str] = []
        for edge in self.edges:
            if edge.kind == "imports" and edge.source == filepath:
                imports.append(edge.target)
        return imports

    def to_text(self) -> str:
        """Compact text representation of the graph for LLM context."""
        lines: list[str] = ["=== CODE DEPENDENCY GRAPH ==="]
        lines.append(f"Nodes: {len(self.nodes)} | Edges: {len(self.edges)}")

        by_file: dict[str, list[CodeNode]] = {}
        for node in self.nodes.values():
            by_file.setdefault(node.file, []).append(node)

        for filepath in sorted(by_file):
            file_nodes = sorted(by_file[filepath], key=lambda n: n.line)
            lines.append(f"\n--- {filepath} ---")
            for node in file_nodes:
                if node.kind == "file":
                    continue
                decorators = node.metadata.get("decorators", [])
                dec_str = f" @{','.join(decorators)}" if decorators else ""
                lines.append(f"  L{node.line} [{node.kind}] {node.name}{dec_str}")

            file_edges = [
                e for e in self.edges
                if e.source == filepath or e.source.startswith(f"{filepath}:")
            ]
            if file_edges:
                for edge in file_edges[:20]:
                    short = edge.target.split(":")[-1] if ":" in edge.target else edge.target
                    lines.append(f"    --{edge.kind}--> {short}")

        return "\n".join(lines)

    def get_statistics(self) -> dict:
        """Return counts by node kind and edge kind."""
        node_kinds: dict[str, int] = {}
        for node in self.nodes.values():
            node_kinds[node.kind] = node_kinds.get(node.kind, 0) + 1
        edge_kinds: dict[str, int] = {}
        for edge in self.edges:
            edge_kinds[edge.kind] = edge_kinds.get(edge.kind, 0) + 1
        return {"nodes": node_kinds, "edges": edge_kinds}

    def _trace_recursive(
        self, name: str, depth: int, path: list[str], results: list[list[str]]
    ) -> None:
        if depth <= 0:
            return
        callers = self.get_callers(name)
        if not callers:
            results.append(path[:])
            return
        for caller_id in callers:
            caller_name = caller_id.split(":")[-1] if ":" in caller_id else caller_id
            if caller_name in path:
                continue
            path.append(caller_name)
            self._trace_recursive(caller_name, depth - 1, path, results)
            path.pop()

    def _add_node(self, node: CodeNode) -> None:
        if node.id not in self.nodes:
            self.nodes[node.id] = node

    def _add_edge(self, edge: CodeEdge) -> None:
        self.edges.append(edge)

    def _parse_python(self, source: str, rel_path: str, file_id: str) -> None:
        """Parse Python source using the ast module."""
        try:
            tree = ast.parse(source, filename=rel_path)
        except SyntaxError:
            return

        for node in ast.iter_child_nodes(tree):
            if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef)):
                func_id = f"{file_id}:{node.name}"
                decorators = [
                    d.attr if isinstance(d, ast.Attribute) else (d.id if isinstance(d, ast.Name) else str(d))
                    for d in node.decorator_list
                ]
                self._add_node(CodeNode(
                    id=func_id, kind="function", name=node.name,
                    file=rel_path, line=node.lineno,
                    metadata={"decorators": decorators},
                ))
                self._add_edge(CodeEdge(source=file_id, target=func_id, kind="contains"))
                self._collect_calls(node, func_id, file_id)

            elif isinstance(node, ast.ClassDef):
                cls_id = f"{file_id}:{node.name}"
                decorators = [
                    d.attr if isinstance(d, ast.Attribute) else (d.id if isinstance(d, ast.Name) else str(d))
                    for d in node.decorator_list
                ]
                self._add_node(CodeNode(
                    id=cls_id, kind="class", name=node.name,
                    file=rel_path, line=node.lineno,
                    metadata={"decorators": decorators},
                ))
                self._add_edge(CodeEdge(source=file_id, target=cls_id, kind="contains"))
                for base in node.bases:
                    if isinstance(base, ast.Name):
                        self._add_edge(CodeEdge(source=cls_id, target=base.id, kind="inherits"))
                for item in ast.iter_child_nodes(node):
                    if isinstance(item, (ast.FunctionDef, ast.AsyncFunctionDef)):
                        method_id = f"{cls_id}.{item.name}"
                        self._add_node(CodeNode(
                            id=method_id, kind="function", name=item.name,
                            file=rel_path, line=item.lineno,
                        ))
                        self._add_edge(CodeEdge(source=cls_id, target=method_id, kind="contains"))
                        self._collect_calls(item, method_id, file_id)

            elif isinstance(node, (ast.Import, ast.ImportFrom)):
                names = [alias.name for alias in node.names]
                for name in names:
                    self._add_edge(CodeEdge(source=file_id, target=name, kind="imports"))

    def _collect_calls(self, func_node: ast.AST, caller_id: str, file_id: str) -> None:
        """Walk *func_node* and record function calls as edges."""
        for child in ast.walk(func_node):
            if isinstance(child, ast.Call):
                name = None
                if isinstance(child.func, ast.Name):
                    name = child.func.id
                elif isinstance(child.func, ast.Attribute):
                    name = child.func.attr
                if name:
                    self._add_edge(CodeEdge(source=caller_id, target=name, kind="calls"))

    _JS_FUNC_RE = re.compile(
        r"(?:function\s+(\w+)|(?:const|let|var)\s+(\w+)\s*=\s*(?:async\s+)?(?:function|\([^)]*\)\s*=>)|"
        r"(?:async\s+)?(\w+)\s*\([^)]*\)\s*\{)",
        re.MULTILINE,
    )
    _JS_IMPORT_RE = re.compile(
        r"(?:import\s+.*?from\s+['\"]([^'\"]+)['\"]|require\s*\(\s*['\"]([^'\"]+)['\"]\s*\))",
        re.MULTILINE,
    )
    _JS_CALL_RE = re.compile(r"(\w+)\s*\(", re.MULTILINE)

    def _parse_javascript(self, source: str, rel_path: str, file_id: str) -> None:
        """Parse JavaScript/TypeScript source using regex-based heuristics."""
        for m in self._JS_FUNC_RE.finditer(source):
            name = m.group(1) or m.group(2) or m.group(3)
            if not name or name in {"if", "for", "while", "switch", "catch", "return", "throw"}:
                continue
            line = source[: m.start()].count("\n") + 1
            func_id = f"{file_id}:{name}"
            self._add_node(CodeNode(
                id=func_id, kind="function", name=name,
                file=rel_path, line=line,
            ))
            self._add_edge(CodeEdge(source=file_id, target=func_id, kind="contains"))
            body_start = m.end()
            next_match = self._JS_FUNC_RE.search(source, m.end())
            body_end = next_match.start() if next_match else len(source)
            body = source[body_start:body_end]
            for cm in self._JS_CALL_RE.finditer(body):
                callee = cm.group(1)
                if callee not in {"if", "for", "while", "switch", "catch", "return", "throw", "function", "const", "let", "var"}:
                    self._add_edge(CodeEdge(source=func_id, target=callee, kind="calls"))

        for m in self._JS_IMPORT_RE.finditer(source):
            module = m.group(1) or m.group(2)
            if module:
                self._add_edge(CodeEdge(source=file_id, target=module, kind="imports"))