/**
 * @fileoverview Rule to flag on declaring variables already declared in the outer scope
 * @author Ilya Volodin
 */

"use strict";

//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------

const astUtils = require("./utils/ast-utils");

//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------

const FUNC_EXPR_NODE_TYPES = new Set([
	"ArrowFunctionExpression",
	"FunctionExpression",
]);
const CALL_EXPR_NODE_TYPE = new Set(["CallExpression"]);
const FOR_IN_OF_TYPE = /^For(?:In|Of)Statement$/u;
const SENTINEL_TYPE =
	/^(?:(?:Function|Class)(?:Declaration|Expression)|ArrowFunctionExpression|CatchClause|ImportDeclaration|ExportNamedDeclaration)$/u;

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

/** @type {import('../types').Rule.RuleModule} */
module.exports = {
	meta: {
		type: "suggestion",

		defaultOptions: [
			{
				allow: [],
				builtinGlobals: false,
				hoist: "functions",
				ignoreOnInitialization: false,
			},
		],

		docs: {
			description:
				"Disallow variable declarations from shadowing variables declared in the outer scope",
			recommended: false,
			url: "https://eslint.org/docs/latest/rules/no-shadow",
		},

		schema: [
			{
				type: "object",
				properties: {
					builtinGlobals: { type: "boolean" },
					hoist: { enum: ["all", "functions", "never"] },
					allow: {
						type: "array",
						items: {
							type: "string",
						},
					},
					ignoreOnInitialization: { type: "boolean" },
				},
				additionalProperties: false,
			},
		],

		messages: {
			noShadow:
				"'{{name}}' is already declared in the upper scope on line {{shadowedLine}} column {{shadowedColumn}}.",
			noShadowGlobal: "'{{name}}' is already a global variable.",
		},
	},

	create(context) {
		const [{ builtinGlobals, hoist, allow, ignoreOnInitialization }] =
			context.options;
		const sourceCode = context.sourceCode;

		/**
		 * Checks whether or not a given location is inside of the range of a given node.
		 * @param {ASTNode} node An node to check.
		 * @param {number} location A location to check.
		 * @returns {boolean} `true` if the location is inside of the range of the node.
		 */
		function isInRange(node, location) {
			return (
				node && node.range[0] <= location && location <= node.range[1]
			);
		}

		/**
		 * Searches from the current node through its ancestry to find a matching node.
		 * @param {ASTNode} node a node to get.
		 * @param {(node: ASTNode) => boolean} match a callback that checks whether or not the node verifies its condition or not.
		 * @returns {ASTNode|null} the matching node.
		 */
		function findSelfOrAncestor(node, match) {
			let currentNode = node;

			while (currentNode && !match(currentNode)) {
				currentNode = currentNode.parent;
			}
			return currentNode;
		}

		/**
		 * Finds function's outer scope.
		 * @param {Scope} scope Function's own scope.
		 * @returns {Scope} Function's outer scope.
		 */
		function getOuterScope(scope) {
			const upper = scope.upper;

			if (upper.type === "function-expression-name") {
				return upper.upper;
			}
			return upper;
		}

		/**
		 * Checks if a variable and a shadowedVariable have the same init pattern ancestor.
		 * @param {Object} variable a variable to check.
		 * @param {Object} shadowedVariable a shadowedVariable to check.
		 * @returns {boolean} Whether or not the variable and the shadowedVariable have the same init pattern ancestor.
		 */
		function isInitPatternNode(variable, shadowedVariable) {
			const outerDef = shadowedVariable.defs[0];

			if (!outerDef) {
				return false;
			}

			const { variableScope } = variable.scope;

			if (
				!(
					FUNC_EXPR_NODE_TYPES.has(variableScope.block.type) &&
					getOuterScope(variableScope) === shadowedVariable.scope
				)
			) {
				return false;
			}

			const fun = variableScope.block;
			const { parent } = fun;

			const callExpression = findSelfOrAncestor(parent, node =>
				CALL_EXPR_NODE_TYPE.has(node.type),
			);

			if (!callExpression) {
				return false;
			}

			let node = outerDef.name;
			const location = callExpression.range[1];

			while (node) {
				if (node.type === "VariableDeclarator") {
					if (isInRange(node.init, location)) {
						return true;
					}
					if (
						FOR_IN_OF_TYPE.test(node.parent.parent.type) &&
						isInRange(node.parent.parent.right, location)
					) {
						return true;
					}
					break;
				} else if (node.type === "AssignmentPattern") {
					if (isInRange(node.right, location)) {
						return true;
					}
				} else if (SENTINEL_TYPE.test(node.type)) {
					break;
				}

				node = node.parent;
			}

			return false;
		}

		/**
		 * Check if variable name is allowed.
		 * @param {ASTNode} variable The variable to check.
		 * @returns {boolean} Whether or not the variable name is allowed.
		 */
		function isAllowed(variable) {
			return allow.includes(variable.name);
		}

		/**
		 * Checks if a variable of the class name in the class scope of ClassDeclaration.
		 *
		 * ClassDeclaration creates two variables of its name into its outer scope and its class scope.
		 * So we should ignore the variable in the class scope.
		 * @param {Object} variable The variable to check.
		 * @returns {boolean} Whether or not the variable of the class name in the class scope of ClassDeclaration.
		 */
		function isDuplicatedClassNameVariable(variable) {
			const block = variable.scope.block;

			return (
				block.type === "ClassDeclaration" &&
				block.id === variable.identifiers[0]
			);
		}

		/**
		 * Checks if a variable is inside the initializer of scopeVar.
		 *
		 * To avoid reporting at declarations such as `var a = function a() {};`.
		 * But it should report `var a = function(a) {};` or `var a = function() { function a() {} };`.
		 * @param {Object} variable The variable to check.
		 * @param {Object} scopeVar The scope variable to look for.
		 * @returns {boolean} Whether or not the variable is inside initializer of scopeVar.
		 */
		function isOnInitializer(variable, scopeVar) {
			const outerScope = scopeVar.scope;
			const outerDef = scopeVar.defs[0];
			const outer = outerDef && outerDef.parent && outerDef.parent.range;
			const innerScope = variable.scope;
			const innerDef = variable.defs[0];
			const inner = innerDef && innerDef.name.range;

			return (
				outer &&
				inner &&
				outer[0] < inner[0] &&
				inner[1] < outer[1] &&
				((innerDef.type === "FunctionName" &&
					innerDef.node.type === "FunctionExpression") ||
					innerDef.node.type === "ClassExpression") &&
				outerScope === innerScope.upper
			);
		}

		/**
		 * Get a range of a variable's identifier node.
		 * @param {Object} variable The variable to get.
		 * @returns {Array|undefined} The range of the variable's identifier node.
		 */
		function getNameRange(variable) {
			const def = variable.defs[0];

			return def && def.name.range;
		}

		/**
		 * Get declared line and column of a variable.
		 * @param {eslint-scope.Variable} variable The variable to get.
		 * @returns {Object} The declared line and column of the variable.
		 */
		function getDeclaredLocation(variable) {
			const identifier = variable.identifiers[0];
			let obj;

			if (identifier) {
				obj = {
					global: false,
					line: identifier.loc.start.line,
					column: identifier.loc.start.column + 1,
				};
			} else {
				obj = {
					global: true,
				};
			}
			return obj;
		}

		/**
		 * Checks if a variable is in TDZ of scopeVar.
		 * @param {Object} variable The variable to check.
		 * @param {Object} scopeVar The variable of TDZ.
		 * @returns {boolean} Whether or not the variable is in TDZ of scopeVar.
		 */
		function isInTdz(variable, scopeVar) {
			const outerDef = scopeVar.defs[0];
			const inner = getNameRange(variable);
			const outer = getNameRange(scopeVar);

			return (
				inner &&
				outer &&
				inner[1] < outer[0] &&
				// Excepts FunctionDeclaration if is {"hoist":"function"}.
				(hoist !== "functions" ||
					!outerDef ||
					outerDef.node.type !== "FunctionDeclaration")
			);
		}

		/**
		 * Checks the current context for shadowed variables.
		 * @param {Scope} scope Fixme
		 * @returns {void}
		 */
		function checkForShadows(scope) {
			const variables = scope.variables;

			for (let i = 0; i < variables.length; ++i) {
				const variable = variables[i];

				// Skips "arguments" or variables of a class name in the class scope of ClassDeclaration.
				if (
					variable.identifiers.length === 0 ||
					isDuplicatedClassNameVariable(variable) ||
					isAllowed(variable)
				) {
					continue;
				}

				// Gets shadowed variable.
				const shadowed = astUtils.getVariableByName(
					scope.upper,
					variable.name,
				);

				if (
					shadowed &&
					(shadowed.identifiers.length > 0 ||
						(builtinGlobals && "writeable" in shadowed)) &&
					!isOnInitializer(variable, shadowed) &&
					!(
						ignoreOnInitialization &&
						isInitPatternNode(variable, shadowed)
					) &&
					!(hoist !== "all" && isInTdz(variable, shadowed))
				) {
					const location = getDeclaredLocation(shadowed);
					const messageId = location.global
						? "noShadowGlobal"
						: "noShadow";
					const data = { name: variable.name };

					if (!location.global) {
						data.shadowedLine = location.line;
						data.shadowedColumn = location.column;
					}
					context.report({
						node: variable.identifiers[0],
						messageId,
						data,
					});
				}
			}
		}

		return {
			"Program:exit"(node) {
				const globalScope = sourceCode.getScope(node);
				const stack = globalScope.childScopes.slice();

				while (stack.length) {
					const scope = stack.pop();

					stack.push(...scope.childScopes);
					checkForShadows(scope);
				}
			},
		};
	},
};
