// Copyright 2024, Command Line Inc.
// SPDX-License-Identifier: Apache-2.0

import {
    addChildAt,
    addIntermediateNode,
    balanceNode,
    findNextInsertLocation,
    findNode,
    findParent,
    removeChild,
} from "./layoutNode.js";
import {
    LayoutNode,
    LayoutTreeAction,
    LayoutTreeActionType,
    LayoutTreeComputeMoveNodeAction,
    LayoutTreeDeleteNodeAction,
    LayoutTreeInsertNodeAction,
    LayoutTreeMoveNodeAction,
    LayoutTreeState,
    MoveOperation,
} from "./model.js";
import { DropDirection, FlexDirection, lazy } from "./utils.js";

/**
 * Initializes a layout tree state.
 * @param rootNode The root node for the tree.
 * @returns The state of the tree.
 *
 * @template T The type of data associated with the nodes of the tree.
 */
export function newLayoutTreeState<T>(rootNode: LayoutNode<T>): LayoutTreeState<T> {
    const { node: balancedRootNode, leafs } = balanceNode(rootNode);
    return {
        rootNode: balancedRootNode,
        leafs,
        pendingAction: undefined,
    };
}

/**
 * Performs a specified action on the layout tree state. Uses Immer Produce internally to resolve deep changes to the tree.
 *
 * @param layoutTreeState The state of the tree.
 * @param action The action to perform.
 *
 * @template T The type of data associated with the nodes of the tree.
 * @returns The new state of the tree.
 */
export function layoutTreeStateReducer<T>(
    layoutTreeState: LayoutTreeState<T>,
    action: LayoutTreeAction
): LayoutTreeState<T> {
    layoutTreeStateReducerInner(layoutTreeState, action);
    return layoutTreeState;
}

/**
 * Helper function for layoutTreeStateReducer.
 * @param layoutTreeState The state of the tree.
 * @param action The action to perform.
 * @see layoutTreeStateReducer
 * @template T The type of data associated with the nodes of the tree.
 */
function layoutTreeStateReducerInner<T>(layoutTreeState: LayoutTreeState<T>, action: LayoutTreeAction) {
    switch (action.type) {
        case LayoutTreeActionType.ComputeMove:
            computeMoveNode(layoutTreeState, action as LayoutTreeComputeMoveNodeAction<T>);
            break;
        case LayoutTreeActionType.CommitPendingAction:
            if (!layoutTreeState?.pendingAction) {
                console.error("unable to commit pending action, does not exist");
                break;
            }
            layoutTreeStateReducerInner(layoutTreeState, layoutTreeState.pendingAction);
            break;
        case LayoutTreeActionType.Move:
            moveNode(layoutTreeState, action as LayoutTreeMoveNodeAction<T>);
            break;
        case LayoutTreeActionType.InsertNode:
            insertNode(layoutTreeState, action as LayoutTreeInsertNodeAction<T>);
            break;
        case LayoutTreeActionType.DeleteNode:
            deleteNode(layoutTreeState, action as LayoutTreeDeleteNodeAction);
            break;
        default: {
            console.error("Invalid reducer action", layoutTreeState, action);
        }
    }
}

/**
 * Computes an operation for inserting a new node into the tree in the given direction relative to the specified node.
 *
 * @param layoutTreeState The state of the tree.
 * @param computeInsertAction The operation to compute.
 *
 * @template T The type of data associated with the nodes of the tree.
 */
function computeMoveNode<T>(
    layoutTreeState: LayoutTreeState<T>,
    computeInsertAction: LayoutTreeComputeMoveNodeAction<T>
) {
    const rootNode = layoutTreeState.rootNode;
    const { node, nodeToMove, direction } = computeInsertAction;
    console.log("computeInsertOperation start", layoutTreeState.rootNode, node, nodeToMove, direction);
    if (direction === undefined) {
        console.warn("No direction provided for insertItemInDirection");
        return;
    }

    let newOperation: MoveOperation<T>;
    const parent = lazy(() => findParent(rootNode, node.id));
    const indexInParent = lazy(() => parent()?.children.findIndex((child) => node.id === child.id));
    const isRoot = rootNode.id === node.id;

    switch (direction) {
        case DropDirection.Top:
            if (node.flexDirection === FlexDirection.Column) {
                newOperation = { parentId: node.id, index: 0, node: nodeToMove };
            } else {
                if (isRoot)
                    newOperation = {
                        node: nodeToMove,
                        index: 0,
                        insertAtRoot: true,
                    };

                const parentNode = parent();
                if (parentNode)
                    newOperation = {
                        parentId: parentNode.id,
                        index: indexInParent() ?? 0,
                        node: nodeToMove,
                    };
            }
            break;
        case DropDirection.Bottom:
            if (node.flexDirection === FlexDirection.Column) {
                newOperation = { parentId: node.id, index: 1, node: nodeToMove };
            } else {
                if (isRoot)
                    newOperation = {
                        node: nodeToMove,
                        index: 1,
                        insertAtRoot: true,
                    };

                const parentNode = parent();
                if (parentNode)
                    newOperation = {
                        parentId: parentNode.id,
                        index: indexInParent() + 1,
                        node: nodeToMove,
                    };
            }
            break;
        case DropDirection.Left:
            if (node.flexDirection === FlexDirection.Row) {
                newOperation = { parentId: node.id, index: 0, node: nodeToMove };
            } else {
                const parentNode = parent();
                if (parentNode)
                    newOperation = {
                        parentId: parentNode.id,
                        index: indexInParent(),
                        node: nodeToMove,
                    };
            }
            break;
        case DropDirection.Right:
            if (node.flexDirection === FlexDirection.Row) {
                newOperation = { parentId: node.id, index: 1, node: nodeToMove };
            } else {
                const parentNode = parent();
                if (parentNode)
                    newOperation = {
                        parentId: parentNode.id,
                        index: indexInParent() + 1,
                        node: nodeToMove,
                    };
            }
            break;
        default:
            throw new Error("Invalid direction");
    }

    if (newOperation) layoutTreeState.pendingAction = { type: LayoutTreeActionType.Move, ...newOperation };
}

function moveNode<T>(layoutTreeState: LayoutTreeState<T>, action: LayoutTreeMoveNodeAction<T>) {
    const rootNode = layoutTreeState.rootNode;
    console.log("moveNode", action, layoutTreeState.rootNode);
    if (!action) {
        console.error("no move node action provided");
        return;
    }
    if (action.parentId && action.insertAtRoot) {
        console.error("parent and insertAtRoot cannot both be defined in a move node action");
        return;
    }

    let node = findNode(rootNode, action.node.id) ?? action.node;
    let parent = findNode(rootNode, action.parentId);
    let oldParent = findParent(rootNode, action.node.id);

    console.log(node, parent, oldParent);

    // Remove nodeToInsert from its old parent
    if (oldParent) {
        removeChild(oldParent, node);
    }

    if (!parent && action.insertAtRoot) {
        addIntermediateNode(rootNode);
        addChildAt(rootNode, action.index, node);
    } else if (parent) {
        addChildAt(parent, action.index, node);
    } else {
        throw new Error("Invalid InsertOperation");
    }
    const { node: newRootNode, leafs } = balanceNode(layoutTreeState.rootNode);
    layoutTreeState.rootNode = newRootNode;
    layoutTreeState.leafs = leafs;
    layoutTreeState.pendingAction = undefined;
}

function insertNode<T>(layoutTreeState: LayoutTreeState<T>, action: LayoutTreeInsertNodeAction<T>) {
    if (!action?.node) {
        console.error("no insert node action provided");
        return;
    }
    if (!layoutTreeState.rootNode) {
        const { node: balancedNode, leafs } = balanceNode(action.node);
        layoutTreeState.rootNode = balancedNode;
        layoutTreeState.leafs = leafs;
        return;
    }
    const insertLoc = findNextInsertLocation(layoutTreeState.rootNode, 5);
    addChildAt(insertLoc.node, insertLoc.index, action.node);
    const { node: newRootNode, leafs } = balanceNode(layoutTreeState.rootNode);
    layoutTreeState.rootNode = newRootNode;
    layoutTreeState.leafs = leafs;
}

function deleteNode<T>(layoutTreeState: LayoutTreeState<T>, action: LayoutTreeDeleteNodeAction) {
    console.log("deleteNode", layoutTreeState, action);
    if (!action?.nodeId) {
        console.error("no delete node action provided");
        return;
    }
    if (!layoutTreeState.rootNode) {
        console.error("no root node");
        return;
    }
    if (layoutTreeState.rootNode.id === action.nodeId) {
        layoutTreeState.rootNode = undefined;
        layoutTreeState.leafs = undefined;
        return;
    }
    const parent = findParent(layoutTreeState.rootNode, action.nodeId);
    if (parent) {
        const node = parent.children.find((child) => child.id === action.nodeId);
        removeChild(parent, node);
        console.log("node deleted", parent, node);
    } else {
        console.error("unable to delete node, not found in tree");
    }
    const { node: newRootNode, leafs } = balanceNode(layoutTreeState.rootNode);
    layoutTreeState.rootNode = newRootNode;
    layoutTreeState.leafs = leafs;
}