import Testing
import Foundation
@testable import CalcPad

@Suite("RustCalculationEngine Tests")
struct RustEngineTests {
    let engine = RustCalculationEngine()

    // MARK: - AC: evaluateLine returns LineResult (not raw pointer)

    @Test("evaluateLine 2+2 returns LineResult with result 4")
    func evalLineBasicArithmetic() {
        let result = engine.evaluateLine("2 + 2")
        #expect(result.result == "4")
        #expect(result.isError == false)
        #expect(result.lineNumber == 1)
    }

    @Test("evaluateLine multiplication")
    func evalLineMultiplication() {
        let result = engine.evaluateLine("6 * 7")
        #expect(result.result == "42")
        #expect(result.isError == false)
    }

    @Test("evaluateLine subtraction")
    func evalLineSubtraction() {
        let result = engine.evaluateLine("10 - 4")
        #expect(result.result == "6")
        #expect(result.isError == false)
    }

    @Test("evaluateLine division")
    func evalLineDivision() {
        let result = engine.evaluateLine("15 / 3")
        #expect(result.result == "5")
        #expect(result.isError == false)
    }

    @Test("evaluateLine decimal result")
    func evalLineDecimal() {
        let result = engine.evaluateLine("7 / 2")
        #expect(result.result == "3.5")
        #expect(result.isError == false)
    }

    // MARK: - AC: evaluateSheet returns array of LineResult, one per line

    @Test("evaluateSheet returns one result per line")
    func evalSheetMultiLine() {
        let text = "2 + 2\n\n10 * 3"
        let results = engine.evaluateSheet(text)
        #expect(results.count == 3)
        #expect(results[0].lineNumber == 1)
        #expect(results[0].result == "4")
        #expect(results[1].lineNumber == 2)
        #expect(results[1].result == nil) // blank line
        #expect(results[2].lineNumber == 3)
        #expect(results[2].result == "30")
    }

    @Test("evaluateSheet with comments and blanks")
    func evalSheetMixed() {
        let text = "// Title\n5 + 5\n\n// Section\n3 * 3"
        let results = engine.evaluateSheet(text)
        #expect(results.count == 5)
        #expect(results[0].result == nil) // comment
        #expect(results[0].isError == false)
        #expect(results[1].result == "10")
        #expect(results[2].result == nil) // blank
        #expect(results[3].result == nil) // comment
        #expect(results[4].result == "9")
    }

    // MARK: - AC: Error handling — errors become LineResult, no crash

    @Test("Malformed expression returns error LineResult, not crash")
    func evalLineError() {
        let result = engine.evaluateLine("2 + + 3")
        #expect(result.isError == true)
        #expect(result.result != nil) // has error message
        #expect(result.result?.starts(with: "Error") == true)
    }

    @Test("Completely invalid input returns error, not crash")
    func evalLineInvalidInput() {
        let result = engine.evaluateLine("@#$%^&")
        // Should not crash — either error or some result
        #expect(result.id == 1)
    }

    // MARK: - AC: Blank and comment lines

    @Test("Blank line returns nil result")
    func blankLine() {
        let result = engine.evaluateLine("")
        #expect(result.result == nil)
        #expect(result.isError == false)
    }

    @Test("Comment with // returns nil result")
    func commentLine() {
        let result = engine.evaluateLine("// this is a comment")
        #expect(result.result == nil)
        #expect(result.isError == false)
    }

    @Test("# is not a comment in Rust engine — treated as identifier lookup")
    func hashNotComment() {
        let result = engine.evaluateLine("# header")
        // The Rust engine does not treat # as a comment. The # is skipped and
        // "header" is parsed as an identifier, resulting in an undefined variable error.
        #expect(result.isError == true)
    }

    // MARK: - AC: Memory safety — no leaks with repeated calls

    @Test("Repeated evaluateLine calls don't leak (1000 iterations)")
    func memoryStressLine() {
        for i in 0..<1000 {
            let result = engine.evaluateLine("\(i) + 1")
            #expect(result.isError == false)
        }
    }

    @Test("Repeated evaluateSheet calls don't leak (100 iterations)")
    func memoryStressSheet() {
        let text = (1...10).map { "\($0) * 2" }.joined(separator: "\n")
        for _ in 0..<100 {
            let results = engine.evaluateSheet(text)
            #expect(results.count == 10)
        }
    }

    // MARK: - AC: Thread safety — concurrent calls

    @Test("Concurrent evaluateLine calls from multiple threads")
    func threadSafety() async {
        await withTaskGroup(of: LineResult.self) { group in
            for i in 0..<50 {
                group.addTask {
                    engine.evaluateLine("\(i) + 1")
                }
            }
            var count = 0
            for await result in group {
                #expect(result.isError == false)
                count += 1
            }
            #expect(count == 50)
        }
    }

    // MARK: - AC: Variables shared across sheet lines

    @Test("evaluateSheet shares variables across lines")
    func evalSheetVariables() {
        let text = "x = 10\nx * 2"
        let results = engine.evaluateSheet(text)
        #expect(results.count == 2)
        #expect(results[0].result == "10")
        #expect(results[1].result == "20")
    }
}