126 lines
2.8 KiB
Go
126 lines
2.8 KiB
Go
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package main
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import (
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"fmt"
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"strconv"
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"strings"
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)
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// domain represents a domain log record
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type domain struct {
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name string
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visits int
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}
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// parser parses a log file and provides an iterator to iterate upon the domains
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//
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// the parser struct is carefully crafted to be usable using its zero values except the map field
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type parser struct {
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sum map[string]int // visits per unique domain
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domains []domain // unique domain names
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total int // total visits to all domains
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lines int // number of parsed lines (for the error messages)
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err error // saves the last error occurred
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}
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// newParser creates and returns a new parser.
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//
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// bare func, it doesn't need to operate on a parser value.
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func newParser() *parser {
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return &parser{sum: make(map[string]int)}
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}
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// PUBLIC METHODS (API)
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// add parses the given line and saves the result to the internal list of
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// domains. it doesn't add the record when the parsing fails.
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//
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// WRITE METHOD
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func (p *parser) add(line string) {
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// if there was a previous error do not add
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if p.err != nil {
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return
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}
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dom, err := p.parse(line)
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// store only the last error
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if err != nil {
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p.err = err
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return
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}
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p.push(dom)
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}
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// iterator returns two functions for iterating over domains.
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// next = returns true when there are more domains to iterate on.
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// cur = returns the current domain
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//
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// READ METHOD
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func (p *parser) iterator() (next func() bool, cur func() domain) {
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// remember the last received line
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var last int
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next = func() bool {
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defer func() { last++ }()
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return len(p.domains) > last
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}
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cur = func() domain {
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d := p.domains[last-1]
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vis := p.sum[d.name]
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// return a copy so the caller cannot change it
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return domain{name: d.name, visits: vis}
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}
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return
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}
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// error returns the last error occurred
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//
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// READ METHOD
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func (p *parser) error() error {
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return p.err
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}
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// PRIVATE METHODS
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// parse parses the given text and returns a domain struct
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//
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// WRITE METHOD
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func (p *parser) parse(line string) (dom domain, err error) {
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p.lines++ // increase the parsed line counter (only write is here)
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fields := strings.Fields(line)
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if len(fields) != 2 {
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err = fmt.Errorf("wrong input: %v (line #%d)", fields, p.lines)
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return dom, err
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}
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name, visits := fields[0], fields[1]
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n, err := strconv.Atoi(visits)
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if n < 0 || err != nil {
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err = fmt.Errorf("wrong input: %q (line #%d)", visits, p.lines)
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return dom, err
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}
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return domain{name: name, visits: n}, nil
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}
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// push pushes the given domain to the internal list of domains.
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// it also increases the total visits for all the domains.
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//
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// WRITE METHOD
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func (p *parser) push(d domain) {
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// collect the unique domains
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if _, ok := p.sum[d.name]; !ok {
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p.domains = append(p.domains, d)
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}
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p.sum[d.name] += d.visits
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p.total += d.visits
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}
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