import Foundation
import SourceKittenFramework
import SwiftSyntax

/// A SwiftLint CorrectableRule that performs its corrections using a SwiftSyntax `SyntaxRewriter`.
public protocol SwiftSyntaxCorrectableRule: SwiftSyntaxRule, CorrectableRule {
    /// Produce a `ViolationsSyntaxRewriter` for the given file.
    ///
    /// - parameter file: The file for which to produce the rewriter.
    ///
    /// - returns: A `ViolationsSyntaxRewriter` for the given file. May be `nil` in which case the rule visitor's
    ///            collected `violationCorrections` will be used.
    func makeRewriter(file: SwiftLintFile) -> ViolationsSyntaxRewriter<ConfigurationType>?
}

public extension SwiftSyntaxCorrectableRule {
    func makeRewriter(file _: SwiftLintFile) -> ViolationsSyntaxRewriter<ConfigurationType>? {
        nil
    }

    func correct(file: SwiftLintFile) -> Int {
        guard let syntaxTree = preprocess(file: file) else {
            return 0
        }
        if let rewriter = makeRewriter(file: file) {
            let newTree = rewriter.visit(syntaxTree)
            file.write(newTree.description)
            return rewriter.numberOfCorrections
        }

        // There is no rewriter. Falling back to the correction ranges collected by the visitor (if any).
        let violations = makeVisitor(file: file)
            .walk(tree: syntaxTree, handler: \.violations)
        guard violations.isNotEmpty else {
            return 0
        }

        let locationConverter = file.locationConverter
        let disabledRegions = file.regions()
            .filter { $0.areRulesDisabled(ruleIDs: Self.description.allIdentifiers) }
            .compactMap { $0.toSourceRange(locationConverter: locationConverter) }

        let correctionRanges = violations
            .filter { !$0.position.isContainedIn(regions: disabledRegions, locationConverter: locationConverter) }
            .compactMap(\.correction)
            .compactMap { correction in
                (
                    startByte: correction.start.utf8Offset,
                    endByte: correction.end.utf8Offset,
                    replacementBytes: correction.replacement.utf8)
            }
            .sorted { $0.startByte > $1.startByte }
        guard correctionRanges.isNotEmpty else {
            return 0
        }

        var bytes = Array(file.contents.utf8)
        for range in correctionRanges {
            bytes.replaceSubrange(range.startByte..<range.endByte, with: range.replacementBytes)
        }
        guard let contents = String(bytes: bytes, encoding: .utf8) else {
            return 0
        }
        file.write(contents)
        return correctionRanges.count
    }
}

/// A SwiftSyntax `SyntaxRewriter` that produces absolute positions where corrections were applied.
open class ViolationsSyntaxRewriter<Configuration: RuleConfiguration>: SyntaxRewriter {
    /// A rule's configuration.
    public let configuration: Configuration
    /// The file from which the traversed syntax tree stems from.
    public let file: SwiftLintFile

    /// A converter of positions in the traversed source file.
    public lazy var locationConverter = file.locationConverter
    /// The regions in the traversed file that are disabled by a command.
    public lazy var disabledRegions = {
        file.regions()
            .filter { $0.areRulesDisabled(ruleIDs: Configuration.Parent.description.allIdentifiers) }
            .compactMap { $0.toSourceRange(locationConverter: locationConverter) }
    }()

    /// The number of corrections made by the rewriter.
    public var numberOfCorrections = 0

    /// Initializer for a ``ViolationsSyntaxRewriter``.
    ///
    /// - Parameters:
    ///   - configuration: Configuration of a rule.
    ///   - file: File from which the syntax tree stems from.
    @inlinable
    public init(configuration: Configuration, file: SwiftLintFile) {
        self.configuration = configuration
        self.file = file
    }

    /// Determines whether the rule is disabled at the start position of the given syntax node.
    ///
    /// - parameter node: The syntax node to check.
    ///
    /// - returns: `true` if the rule is disabled for the node.
    public func isDisabled(atStartPositionOf node: some SyntaxProtocol) -> Bool {
        node.isContainedIn(regions: disabledRegions, locationConverter: locationConverter)
    }

    override open func visitAny(_ node: Syntax) -> Syntax? {
        isDisabled(atStartPositionOf: node) ? node : nil
    }
}