"""
Local (non-forwarded) implementations of LSP features that Bicep.LangServer
(as of 0.46.1) does not implement itself: textDocument/signatureHelp,
textDocument/foldingRange, and workspace/symbol.

These are intentionally simple, regex/bracket-based implementations — good
enough for real editor usage, not a full Bicep parser. They run entirely in
the iLSP proxy and never touch the underlying Bicep LS process.
"""

from __future__ import annotations

import re
from typing import Any

from .bicep_functions import get_signature

_DECL_RE = re.compile(
    r"^\s*(resource|module|var|param|output|func|type)\s+([A-Za-z_][\w]*)",
)

_SYMBOL_KIND = {
    "resource": 6,   # Method-ish; LSP doesn't have a great "resource" kind, use Variable-family
    "module": 2,     # Module
    "var": 13,       # Variable
    "param": 13,     # Variable
    "output": 13,    # Variable
    "func": 12,      # Function
    "type": 5,       # Class
}


# ── signatureHelp ───────────────────────────────────────────────────────────


def _find_enclosing_call(current: str) -> tuple[str, int] | None:
    """
    Walk backwards from the cursor to find the nearest unmatched '(' and the
    identifier immediately preceding it, returning (function_name, arg_index).
    Returns None if the cursor isn't inside a recognizable function call.
    """
    depth = 0
    comma_count = 0
    i = len(current) - 1
    in_string = False
    while i >= 0:
        ch = current[i]
        if ch == "'" and (i == 0 or current[i - 1] != "\\"):
            in_string = not in_string
        elif not in_string:
            if ch in ")]}":
                depth += 1
            elif ch in "(":
                if depth == 0:
                    # Found the opening paren for the innermost call
                    name_m = re.search(r"([A-Za-z_][\w]*)\s*$", current[:i])
                    if name_m:
                        return name_m.group(1), comma_count
                    return None
                depth -= 1
            elif ch in "[{":
                depth -= 1
            elif ch == "," and depth == 0:
                comma_count += 1
        i -= 1
    return None


def compute_signature_help(lines: list[str], line: int, character: int) -> dict[str, Any] | None:
    if line >= len(lines):
        return None
    current = lines[line][:character]
    found = _find_enclosing_call(current)
    if not found:
        return None
    func_name, arg_index = found
    sig = get_signature(func_name)
    if not sig:
        return None

    params = sig["params"]
    parameters = [{"label": p} for p in params] if params else []
    active_param = min(arg_index, max(len(parameters) - 1, 0)) if parameters else 0

    label = f"{func_name}({', '.join(params)})"
    return {
        "signatures": [
            {
                "label": label,
                "documentation": {"kind": "markdown", "value": sig["doc"]},
                "parameters": parameters,
            }
        ],
        "activeSignature": 0,
        "activeParameter": active_param,
    }


# ── foldingRange ────────────────────────────────────────────────────────────


def compute_folding_ranges(lines: list[str]) -> list[dict[str, Any]]:
    """
    Simple stack-based bracket matcher over {}, [], () — collapses any
    multi-line bracket pair into a folding range. Also folds contiguous
    leading '//' comment blocks.
    """
    ranges: list[dict[str, Any]] = []
    stack: list[tuple[str, int]] = []
    in_string = False

    for lineno, text in enumerate(lines):
        i = 0
        while i < len(text):
            ch = text[i]
            if ch == "'" and (i == 0 or text[i - 1] != "\\"):
                in_string = not in_string
            elif not in_string:
                if ch in "{[(":
                    stack.append((ch, lineno))
                elif ch in "}])":
                    if stack:
                        _open_ch, open_line = stack.pop()
                        if lineno > open_line:
                            ranges.append({"startLine": open_line, "endLine": lineno, "kind": "region"})
            i += 1

    # Fold contiguous line-comment blocks (3+ lines)
    i = 0
    while i < len(lines):
        if lines[i].strip().startswith("//"):
            start = i
            while i < len(lines) and lines[i].strip().startswith("//"):
                i += 1
            if i - start >= 3:
                ranges.append({"startLine": start, "endLine": i - 1, "kind": "comment"})
        else:
            i += 1

    ranges.sort(key=lambda r: (r["startLine"], r["endLine"]))
    return ranges


# ── workspace/symbol ────────────────────────────────────────────────────────


def compute_workspace_symbols(docs: dict[str, list[str]], query: str) -> list[dict[str, Any]]:
    """
    Best-effort workspace symbol search over documents currently open in this
    editor session (iLSP has no full-workspace index — only what the client
    has opened). Matches top-level resource/module/var/param/output/func/type
    declarations whose name contains the query (case-insensitive).
    """
    query_l = query.lower()
    results: list[dict[str, Any]] = []
    for uri, lines in docs.items():
        for lineno, text in enumerate(lines):
            m = _DECL_RE.match(text)
            if not m:
                continue
            kind_word, name = m.group(1), m.group(2)
            if query_l and query_l not in name.lower():
                continue
            start_char = text.index(name, m.end(1))
            results.append({
                "name": name,
                "kind": _SYMBOL_KIND.get(kind_word, 13),
                "location": {
                    "uri": uri,
                    "range": {
                        "start": {"line": lineno, "character": start_char},
                        "end": {"line": lineno, "character": start_char + len(name)},
                    },
                },
                "containerName": kind_word,
            })
    return results