import { StreamLanguage } from '@codemirror/language'

/** Simple PlantUML stream parser for syntax highlighting in CodeMirror */
const plantumlParser = StreamLanguage.define({
    name: 'plantuml',
    token(stream) {
        // Single-quote line comment (PlantUML)
        if (stream.match(/^'/)) {
            stream.skipToEnd()
            return 'comment'
        }
        // Double-quoted string
        if (stream.match(/^"/)) {
            let escaped = false
            while (!stream.eol()) {
                if (escaped) {
                    escaped = false
                    stream.next()
                    continue
                }
                const ch = stream.next()
                if (ch === '\\') escaped = true
                else if (ch === '"') break
            }
            return 'string'
        }
        // @directives (@startuml, @enduml, etc.)
        if (stream.match(/^@\w+/)) return 'meta'
        // Skip whitespace
        if (stream.eatSpace()) return null
        // Arrows and connectors
        if (stream.match(/^->>?|<-<?|-->>?|<<--?|<-?>/)) return 'keyword'
        // Keywords (participant, actor, as, title, etc.)
        if (stream.match(/^(participant|actor|as|title|autonumber|left|right|of|over|activate|deactivate|destroy|create|group|opt|alt|else|loop|par|end|note|legend|skinparam|start|stop|if|endif|elseif|while|endwhile|repeat|until|switch|case|endswitch|class|interface|enum|package|namespace|abstract|static|extends|implements)\b/i)) return 'keyword'
        // Any other character (identifier, punctuation, etc.)
        stream.next()
        return null
    },
})

export const plantumlLanguage = plantumlParser