import Foundation

struct SwiftCodeGenerator {
    private let fileContentReader: FileContentReader
    private let indentationUnit: String

    init(
        fileContentReader: FileContentReader = FileContentReader(),
        indentationUnit: String = "    "
    ) {
        self.fileContentReader = fileContentReader
        self.indentationUnit = indentationUnit
    }

    func generate(from rootNamespace: NamespaceNode) throws -> String {
        generatedFileBanner() + (try renderNamespace(rootNamespace, depth: 0))
    }
}

private extension SwiftCodeGenerator {
    func generatedFileBanner() -> String {
        """
        // Generated by the Embedder plugin from the "Static Inline" directory.
        // Any manual changes will be overwritten on the next build.

        """ + "\n"
    }

    func renderNamespace(_ namespace: NamespaceNode, depth: Int) throws -> String {
        let openingLine = namespaceOpeningLine(for: namespace, depth: depth)
        let bodyLines = try renderBody(of: namespace, depth: depth + 1)
        let closingLine = namespaceClosingLine(depth: depth)
        return openingLine + bodyLines + closingLine
    }

    func namespaceOpeningLine(for namespace: NamespaceNode, depth: Int) -> String {
        "\(indent(depth: depth))enum \(namespace.name) {\n"
    }

    func namespaceClosingLine(depth: Int) -> String {
        "\(indent(depth: depth))}\n"
    }

    func renderBody(of namespace: NamespaceNode, depth: Int) throws -> String {
        let fileDeclarations = try namespace.files.map { try renderFileDeclaration($0, depth: depth) }
        let nestedNamespaces = try namespace.subNamespaces.map { try renderNamespace($0, depth: depth) }
        return joinWithBlankLines(fileDeclarations + nestedNamespaces)
    }

    func renderFileDeclaration(_ file: EmbeddableFile, depth: Int) throws -> String {
        let propertyName = IdentifierSanitizer.propertyName(fromFilename: file.filename)
        let literal = try renderStringLiteral(for: file, baseIndent: indent(depth: depth))
        return "\(indent(depth: depth))static let \(propertyName): String = \(literal)\n"
    }

    func renderStringLiteral(for file: EmbeddableFile, baseIndent: String) throws -> String {
        let content = try fileContentReader.readTextContent(of: file)
        let rawLiteral = StringLiteralEscaper.rawTripleQuotedLiteral(from: content)
        return indentContinuationLines(of: rawLiteral, by: baseIndent)
    }

    func indentContinuationLines(of literal: String, by baseIndent: String) -> String {
        let lines = literal.components(separatedBy: "\n")
        guard lines.count > 1 else { return literal }
        let firstLine = lines[0]
        let continuationLines = lines.dropFirst().map { "\(baseIndent)\($0)" }
        return ([firstLine] + continuationLines).joined(separator: "\n")
    }

    func joinWithBlankLines(_ declarations: [String]) -> String {
        declarations.joined(separator: "\n")
    }

    func indent(depth: Int) -> String {
        String(repeating: indentationUnit, count: depth)
    }
}