// *****************************************************************************
// Copyright (C) 2018 TypeFox and others.
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License v. 2.0 which is available at
// http://www.eclipse.org/legal/epl-2.0.
//
// This Source Code may also be made available under the following Secondary
// Licenses when the conditions for such availability set forth in the Eclipse
// Public License v. 2.0 are satisfied: GNU General Public License, version 2
// with the GNU Classpath Exception which is available at
// https://www.gnu.org/software/classpath/license.html.
//
// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
// *****************************************************************************

import { expect } from 'chai';
import { MockTreeModel } from './test/mock-tree-model';
import { createTreeTestContainer } from './test/tree-test-container';
import { TreeModel } from './tree-model';
import { SelectableTreeNode, TreeSelection } from './tree-selection';
import { TreeSelectionState } from './tree-selection-state';

namespace TreeSelectionState {

    export interface Expectation {
        readonly focus?: string | undefined;
        readonly selection?: string[];
    }

    export interface Assert {
        readonly nextState: (type: 'default' | 'toggle' | 'range', nodeId: string, expectation?: Expectation) => Assert;
    }

}

const LARGE_FLAT_MOCK_ROOT = (length = 250000) => {
    const children = Array.from({ length }, (_, idx) => ({ 'id': (idx + 1).toString() }));
    return MockTreeModel.Node.toTreeNode({
        'id': 'ROOT',
        'children': [
            ...children
        ]
    });
};

describe('tree-selection-state', () => {

    const model = createTreeModel();
    const findNode = (nodeId: string) => model.getNode(nodeId) as (SelectableTreeNode);

    beforeEach(() => {
        model.root = MockTreeModel.FLAT_MOCK_ROOT();
        expect(model.selectedNodes).to.be.empty;
    });

    it('should remove the selection but not the focus when toggling the one and only selected node', () => {
        newState()
            .nextState('toggle', '1', {
                focus: '1',
                selection: ['1']
            })
            .nextState('toggle', '1', {
                focus: '1',
                selection: []
            });
    });

    it('should keep the focus on the `fromNode` when selecting a range', () => {
        newState()
            .nextState('toggle', '1')
            .nextState('range', '3', {
                focus: '1',
                selection: ['1', '2', '3']
            });
    });

    it('should always have one single focus node when toggling node in a range', () => {
        newState()
            .nextState('toggle', '1')
            .nextState('range', '3')
            .nextState('toggle', '2', {
                focus: '1',
                selection: ['1', '3']
            })
            .nextState('toggle', '2', {
                focus: '1',
                selection: ['1', '2', '3']
            });
    });

    it('should calculate the range from the focus even unselecting a node in the previously created range', () => {
        newState()
            .nextState('toggle', '5')
            .nextState('range', '2', {
                focus: '5',
                selection: ['2', '3', '4', '5']
            })
            .nextState('toggle', '3', {
                focus: '5',
                selection: ['2', '4', '5']
            })
            .nextState('range', '7', {
                focus: '5',
                selection: ['2', '4', '5', '6', '7']
            });
    });

    it('should discard the previous range selection state if the current one has the same focus with other direction', () => {
        newState()
            .nextState('toggle', '4')
            .nextState('range', '1')
            .nextState('range', '6', {
                focus: '4',
                selection: ['4', '5', '6']
            });
    });

    it('should discard the previous range selection state if the current one overlaps the previous one', () => {
        newState()
            .nextState('toggle', '4')
            .nextState('range', '6')
            .nextState('range', '8', {
                focus: '4',
                selection: ['4', '5', '6', '7', '8']
            });
    });

    it('should move the focus to the most recently selected node if the previous selection was a toggle', () => {
        newState()
            .nextState('toggle', '4')
            .nextState('toggle', '5', {
                focus: '5',
                selection: ['4', '5']
            });
    });

    it('should keep the focus on the previous node if the current toggling happens in the most recent range', () => {
        newState()
            .nextState('toggle', '4')
            .nextState('range', '2', {
                focus: '4',
                selection: ['4', '3', '2']
            });
    });

    it('should move the focus to the next toggle node if that is out of the latest range selection', () => {
        newState()
            .nextState('toggle', '3')
            .nextState('range', '5', {
                focus: '3',
                selection: ['3', '4', '5']
            })
            .nextState('toggle', '1', {
                focus: '1',
                selection: ['3', '4', '5', '1']
            });
    });

    it('should not change the focus when removing a selection from an individual node', () => {
        newState()
            .nextState('toggle', '3')
            .nextState('range', '5', {
                focus: '3',
                selection: ['5', '4', '3']
            })
            .nextState('toggle', '1', {
                focus: '1',
                selection: ['1', '5', '4', '3']
            })
            .nextState('toggle', '4', {
                focus: '1',
                selection: ['1', '5', '3']
            });
    });

    it('should discard the previously selected range if each node from the previous range is contained in the current one', () => {
        newState()
            .nextState('toggle', '5')
            .nextState('range', '2')
            .nextState('toggle', '3', {
                focus: '5',
                selection: ['5', '4', '2']
            })
            .nextState('range', '1', {
                focus: '5',
                selection: ['5', '4', '3', '2', '1']
            })
            .nextState('range', '7', {
                focus: '5',
                selection: ['5', '6', '7']
            });
    });

    it('should be possible to remove the selection of a node which is contained in two overlapping ranges', () => {
        newState()
            .nextState('toggle', '5')
            .nextState('range', '4')
            .nextState('toggle', '3')
            .nextState('range', '2', {
                focus: '3',
                selection: ['2', '3', '4', '5']
            })
            .nextState('range', '5', {
                focus: '3',
                selection: ['5', '4', '3']
            })
            .nextState('toggle', '4', {
                focus: '3',
                selection: ['5', '3']
            });
    });

    it('should be possible to traverse with range selections', () => {
        newState()
            .nextState('toggle', '2')
            .nextState('range', '3', {
                focus: '2', // In VSCode this is 3.
                selection: ['2', '3']
            })
            .nextState('range', '4', {
                focus: '2', // In VSCode this is 4. They distinguish between `Shift + Up Arrow` and `Shift + Click`.
                selection: ['2', '3', '4']
            });
    });

    it('should remove the selection from a node inside a range instead of setting the focus', () => {
        newState()
            .nextState('toggle', '2')
            .nextState('range', '3', {
                focus: '2',
                selection: ['2', '3']
            })
            .nextState('toggle', '5', {
                focus: '5',
                selection: ['2', '3', '5']
            })
            .nextState('range', '6', {
                focus: '5',
                selection: ['2', '3', '5', '6']
            })
            .nextState('toggle', '3', {
                focus: '5',
                selection: ['2', '5', '6']
            });
    });

    it('should merge all individual selections into a range', () => {
        newState()
            .nextState('toggle', '1')
            .nextState('toggle', '3')
            .nextState('toggle', '6')
            .nextState('toggle', '2')
            .nextState('range', '7', {
                focus: '2',
                selection: ['1', '2', '3', '4', '5', '6', '7']
            });
    });

    it('should keep focus on the most recent even when removing selection from individual nodes', () => {
        newState()
            .nextState('toggle', '9')
            .nextState('range', '6', {
                focus: '9',
                selection: ['9', '8', '7', '6']
            })
            .nextState('range', '10', {
                focus: '9',
                selection: ['9', '10']
            })
            .nextState('range', '2', {
                focus: '9',
                selection: ['9', '8', '7', '6', '5', '4', '3', '2']
            })
            .nextState('toggle', '4', {
                focus: '9',
                selection: ['9', '8', '7', '6', '5', '3', '2']
            })
            .nextState('toggle', '5', {
                focus: '9',
                selection: ['9', '8', '7', '6', '3', '2']
            })
            .nextState('toggle', '6', {
                focus: '9',
                selection: ['9', '8', '7', '3', '2']
            })
            .nextState('toggle', '7', {
                focus: '9',
                selection: ['9', '8', '3', '2']
            })
            .nextState('range', '5', {
                focus: '9',
                selection: ['9', '8', '7', '6', '5', '3', '2']
            });
    });

    it('should expand the range instead of discarding it if individual elements have created a hole in the range', () => {
        newState()
            .nextState('toggle', '9')
            .nextState('range', '3', {
                focus: '9',
                selection: ['9', '8', '7', '6', '5', '4', '3']
            })
            .nextState('toggle', '4', {
                focus: '9',
                selection: ['9', '8', '7', '6', '5', '3']
            })
            .nextState('range', '10', {
                focus: '9',
                selection: ['10', '9', '8', '7', '6', '5', '3']
            });
    });

    it('should reset the selection state and the focus when using the default selection', () => {
        newState()
            .nextState('toggle', '1')
            .nextState('toggle', '2', {
                focus: '2',
                selection: ['1', '2']
            })
            .nextState('default', '2', {
                focus: '2',
                selection: ['2']
            })
            .nextState('toggle', '1', {
                focus: '1',
                selection: ['1', '2']
            })
            .nextState('default', '2', {
                focus: '2',
                selection: ['2']
            });
    });

    it('should remove the selection but keep the focus when toggling the single selected node', () => {
        newState()
            .nextState('toggle', '1', {
                focus: '1',
                selection: ['1']
            })
            .nextState('toggle', '1', {
                focus: '1',
                selection: []
            });
    });

    it('should treat ranges with the same from and to node as a single element range', () => {
        newState()
            .nextState('toggle', '2')
            .nextState('range', '1', {
                focus: '2',
                selection: ['1', '2']
            })
            .nextState('range', '2', {
                focus: '2',
                selection: ['2']
            })
            .nextState('range', '3', {
                focus: '2',
                selection: ['2', '3']
            })
            .nextState('range', '2', {
                focus: '2',
                selection: ['2']
            })
            .nextState('range', '1', {
                focus: '2',
                selection: ['1', '2']
            });
    });

    it('should remember the most recent range selection start after toggling individual nodes', () => {
        newState()
            .nextState('toggle', '10', {
                focus: '10',
                selection: ['10']
            })
            .nextState('range', '3', {
                focus: '10',
                selection: ['3', '4', '5', '6', '7', '8', '9', '10']
            })
            .nextState('toggle', '7', {
                focus: '10',
                selection: ['3', '4', '5', '6', '8', '9', '10']
            })
            .nextState('toggle', '8', {
                focus: '10',
                selection: ['3', '4', '5', '6', '9', '10']
            })
            .nextState('toggle', '6', {
                focus: '10',
                selection: ['3', '4', '5', '9', '10']
            })
            .nextState('toggle', '5', {
                focus: '10',
                selection: ['3', '4', '9', '10']
            })
            .nextState('range', '2', {
                focus: '10',
                selection: ['2', '3', '4', '5', '6', '7', '8', '9', '10']
            });
    });

    it('should be able to handle range selection on large tree', () => {
        model.root = LARGE_FLAT_MOCK_ROOT();
        expect(model.selectedNodes).to.be.empty;

        const start = 10;
        const end = 20;
        newState()
            .nextState('toggle', start.toString(), {
                focus: start.toString(),
                selection: [start.toString()]
            })
            .nextState('range', end.toString(), {
                focus: start.toString(),
                selection: Array.from({ length: end - start + 1 }, (_, idx) => (start + idx).toString())
            });
    });

    function newState(): TreeSelectionState.Assert {
        return nextState(new TreeSelectionState(model));
    }

    function nextState(state: TreeSelectionState): TreeSelectionState.Assert {
        return {
            nextState: (nextType, nextId, expectation) => {
                const node = findNode(nextId);
                const type = ((t: 'default' | 'toggle' | 'range') => {
                    switch (t) {
                        case 'default': return TreeSelection.SelectionType.DEFAULT;
                        case 'toggle': return TreeSelection.SelectionType.TOGGLE;
                        case 'range': return TreeSelection.SelectionType.RANGE;
                        default: throw new Error(`Unexpected selection type: ${t}.`);
                    }
                })(nextType);
                const next = state.nextState({ node, type });
                if (!!expectation) {
                    const { focus, selection } = expectation;
                    if ('focus' in expectation) {
                        if (focus === undefined) {
                            expect(next.focus).to.be.undefined;
                        } else {
                            expect(next.focus).to.be.not.undefined;
                            expect(next.focus!.id).to.be.equal(focus);
                            // TODO: we need tree-selection tests too, otherwise, we cannot verify whether there is one focus or not.
                        }
                    }
                    if (selection) {
                        expect(next.selection().map(n => n.id).sort()).to.be.deep.equal(selection.sort());
                    }
                }
                return nextState(next);
            }
        };
    }

    function createTreeModel(): TreeModel {
        return createTreeTestContainer().get(TreeModel);
    }

});