import { shuffleWeightedList, WeightedList } from './weightedList'
import { PRNG } from 'seedrandom'
export type RenderableText = string | WeightedList<string>

export interface TextSource {
    [key: string]: RenderableText
}

export function renderText(text: RenderableText, data: TextSource, rng: PRNG): string {
    const result = shuffleWeightedList(text, '', rng)
    if (needsSubstitution(result)) {
        return substituteText(result, data, rng)
    } else {
        return result
    }
}

const textReplacementRE = /\\(.)|\{\{\s*([A-Za-z0-9_]+)\s*}}/g

function needsSubstitution(text: string): boolean {
    return textReplacementRE.test(text)
}

function substituteText(text: string, data: TextSource, random: PRNG): string {
    return text.replaceAll(
        textReplacementRE,
        (substring, escapedCharacter: string | undefined, fieldName: string | undefined): string => {
            let result: undefined | RenderableText = undefined
            let errType = 'substitution'

            if (typeof escapedCharacter === 'string') {
                if (escapedCharacter === '\\' || escapedCharacter === '{') {
                    result = escapedCharacter
                } else {
                    errType = 'escape'
                }
            }
            if (typeof fieldName === 'string') {
                errType = 'variable or commonText'
                result = data[fieldName]
                if (typeof result === 'string') {
                    if (needsSubstitution(result)) {
                        return substituteText(result, data, random)
                    }
                } else if (typeof result === 'undefined') {
                    errType = 'variable or commonText'
                } else {
                    return renderText(result, data, random)
                }
            }

            if (typeof result === 'undefined') {
                throw Error(`unknown ${errType} ${substring}`)
            }
            return result
        },
    )
}