// Core Part 2 about Code Similarity

//===================================

object C2 { 

// ADD YOUR CODE BELOW

//======================

//(1)

def clean(s: String) : List[String] = """(\w+)""".r.findAllIn(s).toList

//(2)

def occurrences(xs: List[String]): Map[String, Int] = {

    val ls = xs.distinct

    val occLs = for (s <- ls) yield (s, xs.count(_.equals(s)))

    occLs.toMap

}

//(3)

def prod(lst1: List[String], lst2: List[String]) : Int = {

    val occM1 = occurrences(lst1)

    val occM2 = occurrences(lst2)

    (for (s <- occM1) yield s._2 * occM2.getOrElse(s._1,0)).sum

}

//(4)

def overlap(lst1: List[String], lst2: List[String]) : Double = prod(lst1,lst2) / prod(lst1,lst1).max(prod(lst2,lst2))

def similarity(s1: String, s2: String) : Double = overlap(clean(s1), clean(s2))

/* Test cases

val list1 = List("a", "b", "b", "c", "d") 

val list2 = List("d", "b", "d", "b", "d")

occurrences(List("a", "b", "b", "c", "d"))   // Map(a -> 1, b -> 2, c -> 1, d -> 1)

occurrences(List("d", "b", "d", "b", "d"))   // Map(d -> 3, b -> 2)

prod(list1,list2) // 7 

overlap(list1, list2)   // 0.5384615384615384

overlap(list2, list1)   // 0.5384615384615384

overlap(list1, list1)   // 1.0

overlap(list2, list2)   // 1.0

// Plagiarism examples from 

// https://desales.libguides.com/avoidingplagiarism/examples

val orig1 = """There is a strong market demand for eco-tourism in

Australia. Its rich and diverse natural heritage ensures Australia's

capacity to attract international ecotourists and gives Australia a

comparative advantage in the highly competitive tourism industry."""

val plag1 = """There is a high market demand for eco-tourism in

Australia. Australia has a comparative advantage in the highly

competitive tourism industry due to its rich and varied natural

heritage which ensures Australia's capacity to attract international

ecotourists."""

similarity(orig1, plag1) // 0.8679245283018868

// Plagiarism examples from 

// https://www.utc.edu/library/help/tutorials/plagiarism/examples-of-plagiarism.php

val orig2 = """No oil spill is entirely benign. Depending on timing and

location, even a relatively minor spill can cause significant harm to

individual organisms and entire populations. Oil spills can cause

impacts over a range of time scales, from days to years, or even

decades for certain spills. Impacts are typically divided into acute

(short-term) and chronic (long-term) effects. Both types are part of a

complicated and often controversial equation that is addressed after

an oil spill: ecosystem recovery."""

val plag2 = """There is no such thing as a "good" oil spill. If the

time and place are just right, even a small oil spill can cause damage

to sensitive ecosystems. Further, spills can cause harm days, months,

years, or even decades after they occur. Because of this, spills are

usually broken into short-term (acute) and long-term (chronic)

effects. Both of these types of harm must be addressed in ecosystem

recovery: a controversial tactic that is often implemented immediately

following an oil spill."""

overlap(clean(orig2), clean(plag2))  // 0.728

similarity(orig2, plag2)             // 0.728

// The punchline: everything above 0.6 looks suspicious and 

// should be investigated by staff.

*/

}