jscodeshift-switch-transformer

// @ts-check
module.exports = function (fileInfo, api, options) {
    const j = api.jscodeshift
    const ast = j(fileInfo.source);

    const isContainsReducerInName = a => a.value.id.name === 'delayedEmailsReducer';
    const hasTwoNodesInBody = a => a.value.body.length === 2;
    const isSecondElementBreak = a => a.value.body[1].type === 'BreakStatement';
    const isFirstElementExpression = a => a.value.body[0].type === 'ExpressionStatement';
    const isFirstElementAssignment = ({operator, leftName}) => a => {
        const {expression} = a.value.body[0];

        return expression.type === 'AssignmentExpression' && expression.operator === operator && expression.left.name === leftName;
    };
    const updateStateAssign = a => {
        const {expression} = a.value.body[0];
        j(a).replaceWith(j.returnStatement(expression.right))
    };

    ast
        .find(j.FunctionDeclaration)
        .filter(isContainsReducerInName)
        .find(j.SwitchCase)
        .find(j.BlockStatement)
        .filter(hasTwoNodesInBody)
        .filter(isSecondElementBreak)
        .filter(isFirstElementExpression)
        .filter(isFirstElementAssignment({operator: '=', leftName: 'state'}))
        .forEach(updateStateAssign);

    return ast.toSource();
};

module.exports.parser = 'ts';