interfaces: refactor

interfaces/05-log-parser/refactor-notes/refactor-01/changes.md

@@ -0,0 +1,61 @@
+### PROBLEM
++ `main.go` (api client) does a lot of things:
+  + read the log input
+  + parse line by line
+  + updates the results
+  + display the results
+
++ inflexible:
+  + filter by extension (can change)
+  + group by domain (can change) — group by page?
+
+## SOLUTION
++ hide the parsing api from the client
+
++ move `main.go/scanner` -> `parser.go/parse()`
+  + add `main.go`: err handling from `parse()`
+
++ `parser.go/parse()` -> return err directly
+  + remove: `if p.lerr != nil { return }` from parse() and update()
+  + remove: `dumpErrs`
+  + remove: `parser.go/err()`
+  + remove `parser.go/lerr`
+    + return `in.Err()` from `parse()`
+
+  + remove: `p.lines++`
+    + `return r, fmt.Errorf("line %d: %v", p.lines, err)`
+    + remove: `lines int`
+    + `parse()` and `parse()` becomes:
+    ```golang
+    func parse(p *parser, line string) (result, error) {
+        return parseFields(line)
+    }
+
+    func parse(p *parser) {
+        // ...
+        r, err := parse(p, in.Text())
+		if err != nil {
+			return fmt.Errorf("line %d: %v", p.lines, err)
+        }
+        // ...
+    }
+    ```
+
+    + remove `parse()`
+    + call `parseFields` directly in `parse()`:
+    ```go
+	var (
+		l  = 1
+		in = bufio.NewScanner(os.Stdin)
+	)
+
+	for in.Scan() {
+		r, err := parseFields(in.Text())
+		if err != nil {
+			return fmt.Errorf("line %d: %v", l, err)
+		}
+
+		update(p, r)
+		l++
+    }
+    ```