[searcher] Merge Search and SearchVersion (#1117)

## Summary

1. Merge `Search` and `SearchVersion` into `Search` (if version is not
provided, do not use `v=<version>` in search
2. Remove unused `Exists` function

## How was it tested?

devbox search python

Author: hezhizhen

internal/searcher/client.go

@@ -32,31 +32,40 @@ var cachedClient *client
 func Client() *client {
 	if cachedClient == nil {
 		endpoint, _ := url.JoinPath(searchHost(), "search")
+		// TODO: how to handle error
 		cachedClient = &client{
 			endpoint: endpoint,
 		}
 	}
 	return cachedClient
 }
 
-func (c *client) Search(query string) (*SearchResult, error) {
-	return execSearch(c.endpoint + "?q=" + url.QueryEscape(query))
+func (c *client) Search(query string, options ...func() string) (*SearchResult, error) {
+	if query == "" {
+		return nil, fmt.Errorf("query should not be empty")
+	}
+
+	searchURL := c.endpoint + "?q=" + url.QueryEscape(query)
+
+	for _, op := range options {
+		searchURL += op()
+	}
+
+	return execSearch(searchURL)
 }
 
-func (c *client) SearchVersion(query, version string) (*SearchResult, error) {
-	return execSearch(
-		c.endpoint +
-			"?q=" + url.QueryEscape(query) +
-			"&v=" + url.QueryEscape(version),
-	)
+func WithVersion(version string) func() string {
+	return func() string {
+		return "&v=" + url.QueryEscape(version)
+	}
 }
 
 func (c *client) Resolve(pkg string) (*lock.Package, error) {
 	name, version, _ := devpkg.ParseVersionedPackage(pkg)
 	if version == "" {
 		return nil, usererr.New("No version specified for %q.", name)
 	}
-	result, err := c.SearchVersion(name, version)
+	result, err := c.Search(name, WithVersion(version))
 	if err != nil {
 		return nil, err
 	}

internal/searcher/searcher.go

@@ -17,7 +17,7 @@ func SearchAndPrint(w io.Writer, query string) error {
 	c := Client()
 	result, err := c.Search(query)
 	if err != nil {
-		return redact.Errorf("error getting search results: %v", redact.Safe(err))
+		return redact.Errorf("failed to get search results: %v", redact.Safe(err))
 	}
 	if len(result.Results) == 0 {
 		fmt.Fprintf(w, "No results found for %q\n", query)
@@ -39,12 +39,3 @@ func SearchAndPrint(w io.Writer, query string) error {
 	}
 	return nil
 }
-
-func Exists(name, version string) (bool, error) {
-	c := Client()
-	result, err := c.SearchVersion(name, version)
-	if err != nil {
-		return false, err
-	}
-	return len(result.Results) > 0, nil
-}