From 63b5125e6c92d032bac996e6635b44ee8cd2e44f Mon Sep 17 00:00:00 2001
From: xdrm-brackets <doowap31@gmail.com>
Date: Thu, 26 Apr 2018 13:03:44 +0200
Subject: [PATCH] added [internal.uri.parser] for better real-time URI parsing

---
 internal/uri/parser/private.go | 103 +++++++++++++++++++++++++++++++++
 internal/uri/parser/public.go  |  41 +++++++++++++
 internal/uri/parser/types.go   |  35 +++++++++++
 3 files changed, 179 insertions(+)
 create mode 100644 internal/uri/parser/private.go
 create mode 100644 internal/uri/parser/public.go
 create mode 100644 internal/uri/parser/types.go

diff --git a/internal/uri/parser/private.go b/internal/uri/parser/private.go
new file mode 100644
index 0000000..e6066d2
--- /dev/null
+++ b/internal/uri/parser/private.go
@@ -0,0 +1,103 @@
+package parser
+
+import (
+	"fmt"
+)
+
+
+// buildScheme builds a 'basic' scheme
+// from a pattern string
+func buildScheme(ss []string) (Scheme, error) {
+
+	/* (1) Build scheme */
+	sch := make(Scheme, 0, maxMatch)
+
+	for _, s := range ss {
+
+		/* (2) ignore empty */
+		if len(s) == 0 { continue }
+
+		m := new(matcher)
+
+		switch s {
+
+			/* (3) Card: 0, N */
+			case "**":
+				m.req = false
+				m.mul = true
+				sch = append(sch, m)
+
+			/* (4) Card: 1, N */
+			case "..":
+				m.req = true
+				m.mul = true
+				sch = append(sch, m)
+
+			/* (5) Card: 0, 1 */
+			case "*":
+				m.req = false
+				m.mul = false
+				sch = append(sch, m)
+
+			/* (6) Card: 1 */
+			case ".":
+				m.req = true
+				m.mul = false
+				sch = append(sch, m)
+
+			/* (7) Card: 1, literal string */
+			default:
+				m.req = true
+				m.mul = false
+				m.pat = fmt.Sprintf("/%s", s)
+				sch = append(sch, m)
+
+		}
+
+	}
+
+	return sch, nil
+}
+
+
+
+// optimise optimised the scheme for further parsing
+func (s Scheme) optimise() (Scheme, error) {
+
+	/* (1) Nothing to do if only 1 element */
+	if len(s) <= 1 {
+		return s, nil
+	}
+
+	/* (2) Init reshifted scheme */
+	rshift := make(Scheme, 0, maxMatch)
+	rshift = append(rshift, s[0])
+
+
+	/* (2) Iterate over matchers */
+	for p, i, l := 0, 1, len(s) ; i < l ; i++ {
+
+		pre, cur := s[p], s[i]
+
+		/* Merge: 2 following literals */
+		if len(pre.pat) > 0 && len(cur.pat) > 0 {
+
+			// merge strings into previous
+			pre.pat = fmt.Sprintf("%s%s", pre.pat, cur.pat)
+
+			// delete current
+			s[i] = nil
+
+		}
+
+		// increment previous (only if current is not nul)
+		if s[i] != nil {
+			rshift = append(rshift, s[i])
+			p = i
+		}
+
+	}
+
+	return rshift, nil
+
+}
\ No newline at end of file
diff --git a/internal/uri/parser/public.go b/internal/uri/parser/public.go
new file mode 100644
index 0000000..f857591
--- /dev/null
+++ b/internal/uri/parser/public.go
@@ -0,0 +1,41 @@
+package parser
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Build builds an URI scheme from a pattern string
+func Build(s string) (*Scheme, error){
+
+	/* (1) Manage '/' at the start */
+	if len(s) < 1 || s[0] != '/' {
+		return nil, fmt.Errorf("URI must begin with '/'")
+	}
+
+	/* (2) Split by '/' */
+	parts := strings.Split(s, "/")
+
+	/* (3) Max exceeded */
+	if len(parts)-2 > maxMatch {
+		for i, p := range parts {
+			fmt.Printf("%d: '%s'\n", i, p);
+		}
+		return nil, fmt.Errorf("URI must not exceed %d slash-separated components, got %d", maxMatch, len(parts))
+	}
+
+	/* (4) Build for each part */
+	sch, err := buildScheme(parts)
+	if err != nil {
+		return nil, err
+	}
+
+	/* (5) Optimise */
+	opti, err := sch.optimise()
+	if err != nil {
+		return nil, err
+	}
+
+	return &opti, nil
+
+}
\ No newline at end of file
diff --git a/internal/uri/parser/types.go b/internal/uri/parser/types.go
new file mode 100644
index 0000000..6b1c35c
--- /dev/null
+++ b/internal/uri/parser/types.go
@@ -0,0 +1,35 @@
+package parser
+
+// === WILDCARDS ===
+//
+// The star       '*'  -> matches 0 or 1 slash-bounded string
+// The multi star '**' -> matches 0 or more slash-separated strings
+// The dot        '.'  -> matches 1 slash-bounded string
+// The multi dot  '..' -> matches 1 or more slash-separated strings
+//
+// === SCHEME POLICY ===
+//
+// - The last '/' is optional
+// - Any '**' at the very end will match anything that starts with the given prefix
+//
+// === LIMITATIONS ==
+//
+// - A scheme must begin with '/'
+// - A scheme cannot contain something else than a STRING or WILDCARD between 2 '/' separators
+// - A scheme STRING cannot contain the symbols '/' as a character
+// - A scheme STRING containing '*' or '.' characters will be treating as STRING only
+// - A maximum of 16 slash-separated matchers (STRING or WILDCARD) are allowed
+
+const maxMatch = 16
+
+// Represents an URI matcher
+type matcher struct {
+	pat string   // pattern to match (empty if wildcard)
+	req bool     // whether it is required
+	mul bool     // whether multiple matches are allowed
+	buf []string // matched content
+}
+
+
+// Represents an URI scheme
+type Scheme []*matcher
\ No newline at end of file