"""Centralised session-state initialisation for the Streamlit app.

All keys used throughout the app are declared here with their default values.
Calling init_state() at the top of app.py ensures every key exists before any
page tries to read it, preventing KeyError on the first load.
"""

import streamlit as st
from backend.managers.chat_manager import ChatManager


def init_state():
    """Initialise all Streamlit session-state keys with safe defaults.

    Uses ``if key not in st.session_state`` guards throughout so that existing
    values are never overwritten on subsequent reruns — only missing keys are
    set. This means it is safe to call multiple times per session.
    """
    # ── Sidebar state ─────────────────────────────────────────────────────────

    # last_selected tracks the previously clicked tree node to detect new clicks
    # and avoid re-running the same file-open logic on every Streamlit rerender.
    if "last_selected" not in st.session_state:
        st.session_state.last_selected = None

    # Absolute path and workspace-relative path of the currently highlighted folder.
    # Both are set together; both are cleared together when a folder is deselected.
    if "selected_folder" not in st.session_state:
        st.session_state.selected_folder = None

    if "selected_folder_rel" not in st.session_state:
        st.session_state.selected_folder_rel = None

    # ── Chat manager ──────────────────────────────────────────────────────────

    # ChatManager keeps the full conversation history in memory across reruns.
    # Instantiated once and reused so history is not lost on page rerenders.
    if "chat_manager" not in st.session_state:
        st.session_state.chat_manager = ChatManager()

    # ── Editor state ──────────────────────────────────────────────────────────

    # Ordered list of absolute file paths currently open as editor tabs.
    # The list order determines the visual tab order in the UI.
    if "open_files" not in st.session_state:
        st.session_state.open_files = []

    # Dict mapping absolute file path → current editor content (may differ from
    # disk if the user has unsaved changes).
    if "files_content" not in st.session_state:
        st.session_state.files_content = {}

    # Absolute path of the file whose tab is currently active in the editor.
    # Must always be one of the paths in open_files, or None if no file is open.
    if "active_file" not in st.session_state:
        st.session_state.active_file = None

    # Index of the active tab — kept in sync with active_file for st.tabs().
    if "active_tab" not in st.session_state:
        st.session_state.active_tab = 0

    if "is_editing" not in st.session_state:
        st.session_state.is_editing = False

    if "code_suggestions" not in st.session_state:
        st.session_state.code_suggestions = []

    # Output dict from the last code execution: {stdout, stderr, return_code}.
    # Initialised as empty string so the editor view can safely check falsyness.
    if "code_execution_output" not in st.session_state:
        st.session_state.code_execution_output = ""

    # ── Chat state ────────────────────────────────────────────────────────────

    # Flat list of {"role": ..., "content": ...} dicts rendered as chat bubbles.
    # System messages are stored here too but skipped during display.
    if "chat_history" not in st.session_state:
        st.session_state.chat_history = []

    # ── Agent Mode state ──────────────────────────────────────────────────────

    # Boolean toggle — True while the UI is in Coding Agent mode.
    if "agent_mode" not in st.session_state:
        st.session_state.agent_mode = False

    # The live CodingAgent instance while a task is running.
    # Set by _start_agent(), cleared by _reset_agent().
    if "coding_agent" not in st.session_state:
        st.session_state.coding_agent = None

    # Lifecycle state of the agent: "idle" | "waiting_approval" | "done".
    # Controls which sub-screen render_agent_mode() displays.
    if "agent_status" not in st.session_state:
        st.session_state.agent_status = "idle"

    # Chronological list of completed step records shown in the Agent Log expander.
    # Each entry: {"thought": str, "tool": str, "arguments": dict, "result": str}
    if "agent_log" not in st.session_state:
        st.session_state.agent_log = []

    # The action the agent has proposed but that has not yet been approved or
    # rejected by the user.  Stored as the raw dict returned by propose_next_action().
    if "agent_pending_action" not in st.session_state:
        st.session_state.agent_pending_action = None



if __name__ == "__main__":
    init_state()