package main

import (
    "log"
    "testing"
)

type Person struct {
    Name string
    From []*Record
    To   []*Record
}

type Record struct {
    Amount int
    From   *Person
    To     *Person
}

// For all people connected to person B:
//  A -> B : 3,  B -> C: 5      =>  A -> C : 3,  B -> C: 2
// After that no loop could pass through person B
func (p *Person) relax() {
    di := 0
    ci := 0
    for di < len(p.From) && ci < len(p.To) { // 2N
        if p.From[di].Amount == p.To[di].Amount {
            p.From[di].Amount = 0
            p.To[di].Amount = 0
            ci++
            di++
            //TODO: remove edge where amount == 0
        } else if p.From[di].Amount > p.To[di].Amount {
            toDeduce := p.To[di].Amount
            p.From[di].Amount -= toDeduce
            p.To[di].Amount -= toDeduce
            ci++
            //TODO: remove edge where amount == 0
        } else {
            toDeduce := p.From[di].Amount
            p.To[di].Amount -= toDeduce
            p.From[di].Amount -= toDeduce
            di++
            //TODO: remove edge where amount == 0
        }
    }
}

func printState(people []Person) {
    for _, p := range people {
        for _, c := range p.To {
            log.Printf("%v %v-> %v", p.Name, c.Amount, c.To.Name)
        }
    }
}

func TestRelax(t *testing.T) {
    // initialization

    people := []Person{
        {Name: "A"}, {Name: "B"}, {Name: "C"}, {Name: "D"},
    }

    value := 1
    for i := range people {
        for j := range people {
            if i == j {
                continue
            }
            value++
            rec := Record{
                From:   &people[i],
                To:     &people[j],
                Amount: value,
            }
            people[i].To = append(people[i].To, &rec)
            people[j].From = append(people[j].From, &rec)
        }
    }
    log.Print("BEFORE")
    printState(people)
    for i := 0; i < len(people)/2; i++ {
        for _, p := range people {
            p.relax()
        }
    }
    log.Print("AFTER")
    printState(people)
}