Data commit

Task/Inverted-index/Go/inverted-index.go

@@ -0,0 +1,135 @@
+package main
+
+import (
+    "bufio"
+    "bytes"
+    "errors"
+    "fmt"
+    "io"
+    "os"
+)
+
+// inverted index representation
+var index map[string][]int // ints index into indexed
+var indexed []doc
+
+type doc struct {
+    file  string
+    title string
+}
+
+func main() {
+    // initialize representation
+    index = make(map[string][]int)
+
+    // build index
+    if err := indexDir("docs"); err != nil {
+        fmt.Println(err)
+        return
+    }
+
+    // run user interface
+    ui()
+}
+
+func indexDir(dir string) error {
+    df, err := os.Open(dir)
+    if err != nil {
+        return err
+    }
+    fis, err := df.Readdir(-1)
+    if err != nil {
+        return err
+    }
+    if len(fis) == 0 {
+        return errors.New(fmt.Sprintf("no files in %s", dir))
+    }
+    indexed := 0
+    for _, fi := range fis {
+        if !fi.IsDir() {
+            if indexFile(dir + "/" + fi.Name()) {
+                indexed++
+            }
+        }
+    }
+    return nil
+}
+
+func indexFile(fn string) bool {
+    f, err := os.Open(fn)
+    if err != nil {
+        fmt.Println(err)
+        return false // only false return
+    }
+
+    // register new file
+    x := len(indexed)
+    indexed = append(indexed, doc{fn, fn})
+    pdoc := &indexed[x]
+
+    // scan lines
+    r := bufio.NewReader(f)
+    lines := 0
+    for {
+        b, isPrefix, err := r.ReadLine()
+        switch {
+        case err == io.EOF:
+            return true
+        case err != nil:
+            fmt.Println(err)
+            return true
+        case isPrefix:
+            fmt.Printf("%s: unexpected long line\n", fn)
+            return true
+        case lines < 20 && bytes.HasPrefix(b, []byte("Title:")):
+            // in a real program you would write code
+            // to skip the Gutenberg document header
+            // and not index it.
+            pdoc.title = string(b[7:])
+        }
+        // index line of text in b
+        // again, in a real program you would write a much
+        // nicer word splitter.
+    wordLoop:
+        for _, bword := range bytes.Fields(b) {
+            bword := bytes.Trim(bword, ".,-~?!\"'`;:()<>[]{}\\|/=_+*&^%$#@")
+            if len(bword) > 0 {
+                word := string(bword)
+                dl := index[word]
+                for _, d := range dl {
+                    if d == x {
+                        continue wordLoop
+                    }
+                }
+                index[word] = append(dl, x)
+            }
+        }
+    }
+    return true
+}
+
+func ui() {
+    fmt.Println(len(index), "words indexed in", len(indexed), "files")
+    fmt.Println("enter single words to search for")
+    fmt.Println("enter a blank line when done")
+    var word string
+    for {
+        fmt.Print("search word: ")
+        wc, _ := fmt.Scanln(&word)
+        if wc == 0 {
+            return
+        }
+        switch dl := index[word]; len(dl) {
+        case 0:
+            fmt.Println("no match")
+        case 1:
+            fmt.Println("one match:")
+            fmt.Println("   ", indexed[dl[0]].file, indexed[dl[0]].title)
+        default:
+            fmt.Println(len(dl), "matches:")
+            for _, d := range dl {
+                fmt.Println("   ", indexed[d].file, indexed[d].title)
+            }
+        }
+    }
+}