Parse psychometric exam pdf file

psychometricExamParser.kt

package com.yoavst.psychometric

import com.yoavst.resourceOf
import org.apache.pdfbox.pdmodel.PDDocument
import org.apache.pdfbox.text.PDFTextStripper
import org.apache.pdfbox.text.TextPosition

fun main(args: Array<String>) {
    val file = File("psychometric/exam.pdf")
    val document = PDDocument.load(file)
    val indexes = getIndexes(document)
    val answers = getAnswers(document, indexes.first { (name, _) -> name == AnswersPage }.number + 1)

    val chapters = createChapters(indexes, answers)
    val grades = getGrades(document, indexes.first { (name, _) -> name == GradePage }.number + 1)
}

fun getAnswers(document: PDDocument, page: Int): List<Answers> {
    val chapters = mutableListOf<Pair<String, Int>>() // name to y
    val answers = mutableListOf<Pair<String, Int>>()
    val stripper = object : PDFTextStripper() {
        override fun writeString(text: String, textPositions: List<TextPosition>) {
            if (ChapterLine in text)
                chapters += text to textPositions[0].y.toInt()
            else if (AnswersLine in text)
                answers += text.replace(AnswersLine, "").trim() to textPositions[0].y.toInt()
        }
    }
    stripper.startPage = page
    stripper.endPage = page
    stripper.getText(document)
    return answers.map { (data, y) ->
        Answers(
                chapters.sortedByDescending { it.second }.first { (_, chapterY) -> y - chapterY > 0 }.first,
                IntArray(data.length) { data[it] - '0' }
        )
    }
}

fun getIndexes(document: PDDocument): List<Page> {
    val stripper = PDFTextStripper()
    stripper.startPage = 2
    stripper.endPage = 2
    val text = stripper.getText(document)
    return text.split("\r\n").filter { "...." in it }.map { it.replace("[.]{2,}".toRegex(), ".").replace('.', ' ').trim() }.mapNotNull {
        "\\d+".toRegex().find(it)?.let { match ->
            Page(it.removeRange(match.range).trim(), match.value.toInt())
        }
    }
}

fun createChapters(pages: List<Page>, answers: List<Answers>): List<Chapter> {
    return pages.sortedBy(Page::number).let { pages ->
        answers.map { (name, answers) ->
            val mappedName = name.replace(" - ", " ")
            val pageIndex = pages.indexOfFirst { it.name == mappedName }
            Chapter(name, pages[pageIndex].number until pages[pageIndex + 1].number, answers)
        }
    }
}

fun getGrades(document: PDDocument, page: Int): List<Grade> {
    val grades = arrayOfNulls<Grade>(47)
    val stripper = object : PDFTextStripper() {
        override fun writeString(text: String, textPositions: List<TextPosition>) {
            if (text.toLongOrNull()?.takeIf { it != (page - 1).toLong() } != null) {
                var pos = textPositions[0].x
                var rightAnswers: String = textPositions[0].unicode
                var i = 1
                while (i < textPositions.size) {
                    val position = textPositions[i]
                    if (Math.abs(position.x - pos) < 10) {
                        rightAnswers += position.unicode
                        i++
                        pos = position.x
                    } else break
                }

                val leftText = text.substring(rightAnswers.length)
                val numbers = IntArray(3)
                var numbersIndex = 0
                var number = 0
                for (k in leftText.indices) {
                    val temp = number * 10 + (leftText[k] - '0')
                    if (temp > 150) {
                        numbers[numbersIndex++] = number
                        number = (leftText[k] - '0')
                    } else {
                        number = temp
                    }
                }
                numbers[numbersIndex] = number

                grades[rightAnswers.toInt()] = Grade(numbers[0].takeIf { it != 0 }, numbers[1].takeIf { it != 0 }, numbers[2].takeIf { it != 0 })
            }
        }
    }
    stripper.startPage = page
    stripper.endPage = page
    stripper.getText(document)
    return grades.requireNoNulls().toList()
}


data class Page(val name: String, val number: Int)
data class Answers(val name: String, val answers: IntArray) {
    override fun equals(other: Any?): Boolean = other is Answers && other.name == name && other.answers.contentEquals(answers)
    override fun hashCode(): Int = name.hashCode() * 31 + answers.contentHashCode()
}

data class Chapter(val name: String, val pages: IntRange, val answers: IntArray) {
    override fun equals(other: Any?): Boolean = other is Chapter && other.name == name && other.pages == pages && other.answers.contentEquals(answers)
    override fun hashCode(): Int = (name.hashCode() * 31 + pages.hashCode()) * 31 + answers.contentHashCode()
}

data class Grade(val hebrew: Int?, val math: Int?, val english: Int?)

val AnswersPage = "מפתח תשובות נכונות"
val GradePage = "חישוב אומדן ציוני הבחינה"
val ChapterLine = "פרק"
val AnswersLine = "הנכונה"