refactor: Fix linter bugs (#40)

* refactor: Fix linter bugs

* refactor: Reduce cognitive complexity

Author: obalunenko

README.md

@@ -31,7 +31,7 @@ This repository contains solutions for puzzles and cli tool to run solutions to
   <summary>2015</summary>  
 
   - [x] [Day 1: Not Quite Lisp](https://adventofcode.com/2015/day/1)
-  - [ ] [Day 2: I Was Told There Would Be No Math](https://adventofcode.com/2015/day/2)
+  - [x] [Day 2: I Was Told There Would Be No Math](https://adventofcode.com/2015/day/2)
   - [ ] [Day 3: Perfectly Spherical Houses in a Vacuum](https://adventofcode.com/2015/day/3)
   - [ ] [Day 4: The Ideal Stocking Stuffer](https://adventofcode.com/2015/day/4)
   - [ ] [Day 5: Doesn't He Have Intern-Elves For This?](https://adventofcode.com/2015/day/5)

internal/puzzles/solutions/2020/day01/solution.go

@@ -11,6 +11,10 @@ import (
 	"github.com/obalunenko/advent-of-code/internal/puzzles"
 )
 
+func init() {
+	puzzles.Register(solution{})
+}
+
 type solution struct{}
 
 func (s solution) Year() string {
@@ -21,10 +25,6 @@ func (s solution) Day() string {
 	return puzzles.Day01.String()
 }
 
-func init() {
-	puzzles.Register(solution{})
-}
-
 func (s solution) Part1(input io.Reader) (string, error) {
 	scanner := bufio.NewScanner(input)
 
@@ -85,14 +85,22 @@ func (s solution) Part2(input io.Reader) (string, error) {
 
 	sort.Ints(expensereport)
 
+	a, b, c, err := foundEntries(expensereport)
+	if err != nil {
+		return "", fmt.Errorf("found entries: %w", err)
+	}
+
+	res := a * b * c
+
+	return strconv.Itoa(res), nil
+}
+
+func foundEntries(expensereport []int) (a, b, c int, err error) {
 	const (
 		dest = 2020
 	)
 
-	var (
-		a, b, c int
-		found   bool
-	)
+	var found bool
 
 loop:
 	for i := 0; i < len(expensereport)-2; i++ {
@@ -113,10 +121,8 @@ loop:
 	}
 
 	if !found {
-		return "", fmt.Errorf("answer not found")
+		return 0, 0, 0, fmt.Errorf("answer not found")
 	}
 
-	res := a * b * c
-
-	return strconv.Itoa(res), nil
+	return a, b, c, nil
 }

internal/puzzles/solutions/2020/day01/spec.md

@@ -1,4 +1,7 @@
 # --- Day 1: Report Repair ---
+
+## --- Part One ---
+
 After saving Christmas five years in a row, you've decided to take a vacation at a nice resort on a tropical island. 
 Surely, Christmas will go on without you.
 
@@ -33,7 +36,8 @@ Multiplying them together produces `1721 * 299 = 514579`, so the correct answer
 Of course, your expense report is much larger. `Find the two entries that sum to 2020; 
 what do you get if you multiply them together`?
 
---- Part Two ---
+## --- Part Two ---
+
 The Elves in accounting are thankful for your help; one of them even offers you a starfish coin they had left over 
 from a past vacation. They offer you a second one if you can find three numbers in your expense report that meet 
 the same criteria.

internal/puzzles/utils/intcomputer/intcomputer.go

@@ -31,6 +31,9 @@ const (
 	shift = 4
 )
 
+// ErrNotExist returns in case when value not found in memory.
+var ErrNotExist = errors.New("value not exist")
+
 // New creates instance of IntComputer from passed intcode program.
 func New(in io.Reader) (IntComputer, error) {
 	var c IntComputer
@@ -98,12 +101,12 @@ loop:
 func (c *IntComputer) add(aPos, bPos, resPos int) error {
 	a, ok := c.memory[aPos]
 	if !ok {
-		return fmt.Errorf("value not exist [apos:%d]", aPos)
+		return fmt.Errorf("apos:%d: %w", aPos, ErrNotExist)
 	}
 
 	b, ok := c.memory[bPos]
 	if !ok {
-		return fmt.Errorf("value not exist [bpos:%d]", bPos)
+		return fmt.Errorf("bpos:%d: %w", bPos, ErrNotExist)
 	}
 
 	res := a + b
@@ -115,12 +118,12 @@ func (c *IntComputer) add(aPos, bPos, resPos int) error {
 func (c *IntComputer) mult(aPos, bPos, resPos int) error {
 	a, ok := c.memory[aPos]
 	if !ok {
-		return errors.New("value not exist")
+		return ErrNotExist
 	}
 
 	b, ok := c.memory[bPos]
 	if !ok {
-		return errors.New("value not exist")
+		return ErrNotExist
 	}
 
 	res := a * b
@@ -132,7 +135,7 @@ func (c *IntComputer) mult(aPos, bPos, resPos int) error {
 func (c *IntComputer) abort() (int, error) {
 	res, ok := c.memory[0]
 	if !ok {
-		return 0, errors.New("value not exist")
+		return 0, ErrNotExist
 	}
 
 	return res, nil
@@ -150,8 +153,9 @@ func (c *IntComputer) Input(noun, verb int) {
 func (c *IntComputer) Reset() {
 	c.memory = make(map[int]int, len(c.initial))
 
-	for i, n := range c.initial {
-		n := n
+	for i := range c.initial {
+		n := c.initial[i]
+
 		c.memory[i] = n
 	}
 }