export interface CdlEventHandler {
    eventName: string
    parameterNames: string[]
}

function structuralCode(line: string): string {
    let result = ""
    let inString = false
    let escaped = false

    for (const character of line) {
        if (escaped) {
            escaped = false
            result += inString ? " " : character
            continue
        }
        if (character === "\\") {
            escaped = true
            result += inString ? " " : character
            continue
        }
        if (character === '"') {
            inString = !inString
            result += " "
            continue
        }
        if (character === "#" && !inString) {
            break
        }
        result += inString ? " " : character
    }

    return result
}

function braceDelta(line: string): number {
    let delta = 0
    for (const character of structuralCode(line)) {
        if (character === "{") {
            delta += 1
        } else if (character === "}") {
            delta -= 1
        }
    }
    return delta
}

export function cdlEventHandlerAtLine(
    source: string,
    declarationLine: number
): CdlEventHandler | undefined {
    const lines = source.split(/\r?\n/)
    const declaration = lines[declarationLine]
    if (declaration === undefined) {
        return undefined
    }

    const eventMatch = /^\s*EVENT\s+([^\s{]+)/.exec(structuralCode(declaration))
    if (!eventMatch) {
        return undefined
    }

    const parameterNames: string[] = []
    let eventOpened = false
    let depth = 0

    for (let lineNumber = declarationLine; lineNumber < lines.length; lineNumber++) {
        const line = lines[lineNumber]
        const code = structuralCode(line)

        if (eventOpened && depth === 1) {
            const parameterMatch = /^\s*PARAM\s+([^\s{]+)/.exec(code)
            if (parameterMatch) {
                parameterNames.push(parameterMatch[1])
            }
        }

        const delta = braceDelta(line)
        if (!eventOpened && delta > 0) {
            eventOpened = true
        }
        if (eventOpened) {
            depth += delta
            if (depth <= 0) {
                break
            }
        }
    }

    return {
        eventName: eventMatch[1],
        parameterNames
    }
}

function momEventName(eventName: string): string {
    return `MOM_${eventName.replace(/^MOM_/i, "")}`
}

function momVariableName(parameterName: string): string {
    return `mom_${parameterName.replace(/^mom_/i, "")}`
}

export function createCdlEventHandlerSnippet(handler: CdlEventHandler): string {
    const globals = [
        ...new Set(handler.parameterNames.map((parameter) => momVariableName(parameter)))
    ]
    const lines = [`proc ${momEventName(handler.eventName)} { } {`]

    if (globals.length > 0) {
        lines.push(...globals.map((variable) => `    global ${variable}`), "")
    }
    lines.push("    #Put your UDE Handler Tcl here", "", "}")

    return lines.join("\n")
}