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parse.go
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parse.go
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package day19
import (
"fmt"
"strconv"
"strings"
)
type Input struct {
Rules map[RuleID]Rule
Messages []string
}
func ParseInput(in [][]string) (*Input, error) {
if len(in) != 2 {
return nil, fmt.Errorf("day19: expected 2 input blocks, got %d", len(in))
}
rules := make(map[RuleID]Rule)
for _, r := range in[0] {
toks := strings.SplitN(r, ": ", 2)
if len(toks) != 2 {
return nil, fmt.Errorf("day19: can't parse rule: %q", r)
}
ruleID, err := strconv.Atoi(toks[0])
if err != nil {
return nil, fmt.Errorf("day19: atoi: %w", err)
}
rules[RuleID(ruleID)], err = parseRule(toks[1])
if err != nil {
return nil, fmt.Errorf("day19: parsing rule %q: %w", toks[1], err)
}
}
return &Input{
Rules: rules,
Messages: in[1],
}, nil
}
func parseRule(rule string) (Rule, error) {
if strings.Contains(rule, `"`) {
return TerminalRule(rule[1]), nil
}
if strings.Contains(rule, "|") {
toks := strings.Split(rule, " | ")
subrules := make(OrRule, len(toks))
for i := 0; i < len(toks); i++ {
var err error
subrules[i], err = parseRule(toks[i])
if err != nil {
return nil, err
}
}
return subrules, nil
}
if strings.Contains(rule, " ") {
toks := strings.Split(rule, " ")
subrules := make(AdjacentRule, len(toks))
for i := 0; i < len(toks); i++ {
var err error
subrules[i], err = parseRule(toks[i])
if err != nil {
return nil, err
}
}
return subrules, nil
}
ruleID, err := strconv.Atoi(rule)
if err != nil {
return nil, fmt.Errorf("day19: atoi: %w", err)
}
return RefRule(ruleID), nil
}