api: Add go files

I know this is a huge commit, but I can't be bothered to check
this in part by part.

api/comment_vote.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"net/http"
+	"time"
+)
+
+func commentVote(commenterHex string, commentHex string, direction int) error {
+	if commentHex == "" || commenterHex == "" {
+		return errorMissingField
+	}
+
+	statement := `
+    INSERT INTO
+    votes  (commentHex, commenterHex, direction, voteDate)
+    VALUES ($1,         $2,           $3,        $4      )
+    ON CONFLICT (commentHex, commenterHex) DO
+      UPDATE SET direction = $3;
+  `
+	_, err := db.Exec(statement, commentHex, commenterHex, direction, time.Now().UTC())
+	if err != nil {
+		logger.Errorf("error inserting/updating votes: %v", err)
+		return errorInternal
+	}
+
+	return nil
+}
+
+func commentVoteHandler(w http.ResponseWriter, r *http.Request) {
+	type request struct {
+		Session    *string `json:"session"`
+		CommentHex *string `json:"commentHex"`
+		Direction  *int    `json:"direction"`
+	}
+
+	var x request
+	if err := unmarshalBody(r, &x); err != nil {
+		writeBody(w, response{"success": false, "message": err.Error()})
+		return
+	}
+
+	if *x.Session == "anonymous" {
+		writeBody(w, response{"success": false, "message": errorUnauthorisedVote.Error()})
+		return
+	}
+
+	c, err := commenterGetBySession(*x.Session)
+	if err != nil {
+		writeBody(w, response{"success": false, "message": err.Error()})
+		return
+	}
+
+	direction := 0
+	if *x.Direction > 0 {
+		direction = 1
+	} else if *x.Direction < 0 {
+		direction = -1
+	}
+
+	if err := commentVote(c.CommenterHex, *x.CommentHex, direction); err != nil {
+		writeBody(w, response{"success": false, "message": err.Error()})
+		return
+	}
+
+	writeBody(w, response{"success": true})
+}