Got some sloppy DB service support for snippets now.

README.md

@@ -91,6 +91,11 @@ Warning: http.ServeFile() does not automatically sanitize the file path. If you
 
 The Let's-go book calls for MySQL. We use [go-sqlite3](ggithub.com/mattn/go-sqlite3) and [go-migrate]() tool to manage migrations instead. Use `make check-system-deps` to validate all tools for this repository are installed.
 
+Packages to consider adopting include sqlx or https://github.com/blockloop/scan. Both have the potential to reduce the verbosity that comes will using the standard database/sql package.
+
+### Nulls Gotcha
+
+Beware of Nulls when using `DB.Scan()` To avoid issues consider using the sql.Null* types or putting a `NOT NULL` constraint in your DDL. Also a sensible Default
 
 ## Managing Dependencies
 

internal/model/errors.go

@@ -0,0 +1,6 @@
+package model
+
+import "errors"
+
+// TODO migrate this to an apperror
+var ErrNoRecord = errors.New("models: no record found")

internal/model/example.go

@@ -0,0 +1,65 @@
+// This file simply illustrates the use of transactions when performing operations on your sql db.
+package model
+
+import "database/sql"
+
+type ExampleModel struct {
+	DB *sql.DB
+	// Prepared statements
+	//
+	// Prepared statements exist on database connections. Statement objects will therefore attempt to reuse the connection
+	// object from the connection pool that the statement was created on. If the connection was Closed or in use, it will
+	// be re-prepared on a new connection. This can increase load, create more connections than expected. Etc. Really its
+	// and optimization that you may not need to start looking at. When you do you have to look at load test data to get an
+	// idea for how it actually behaves.
+	//
+	// Another pattern is avoid recreated prepared statements on each invocation and instead attach them
+	// to the service instead. This doesn't really work well with transactions which have thier own tx.Prepare
+	// method
+	// InsertStmt *sql.Stmt
+}
+
+// func NewExampleModel(db *sql.DB) (*ExampleModel, error) {
+// 	insertStmt, err := db.Prepare("INSERT INTO example (message, thought) VALUES (?, ?)")
+// 	if err != nil {
+// 		return nil, err
+// 	}
+// 	return &ExampleModel{DB: db, InsertStmt: insertStmt}, nil
+// }
+
+func (m *ExampleModel) ExampleTransaction() error {
+	// Calling the Begin() method on the connection pool creates a new sql.Tx
+	// object, which represents the in-progress database transaction.
+	tx, err := m.DB.Begin()
+	if err != nil {
+		return err
+	}
+
+	// Defer a call to tx.Rollback() to ensure it is always called before the
+	// function returns. If the transaction succeeds it will be already be
+	// committed by the time tx.Rollback() is called, making tx.Rollback() a
+	// no-op. Otherwise, in the event of an error, tx.Rollback() will rollback
+	// the changes before the function returns.
+	defer tx.Rollback()
+
+	// Call Exec() on the transaction, passing in your statement and any
+	// parameters. It's important to notice that tx.Exec() is called on the
+	// transaction object just created, NOT the connection pool. Although we're
+	// using tx.Exec() here you can also use tx.Query() and tx.QueryRow() in
+	// exactly the same way.
+	_, err = tx.Exec("INSERT INTO ...")
+	if err != nil {
+		return err
+	}
+
+	// Carry out another transaction in exactly the same way.
+	_, err = tx.Exec("UPDATE ...")
+	if err != nil {
+		return err
+	}
+
+	// If there are no errors, the statements in the transaction can be committed
+	// to the database with the tx.Commit() method.
+	err = tx.Commit()
+	return err
+}

internal/model/snippets.go

@@ -2,15 +2,18 @@ package model
 
 import (
 	"database/sql"
+	"errors"
 	"fmt"
 	"log/slog"
 	"time"
 )
 
 type Snippet struct {
-	ID        int
-	Title     string
-	Content   string
+	ID int
+	// Title     string
+	// Content   string
+	Title     sql.NullString
+	Content   sql.NullString
 	CreatedAt time.Time
 	UpdatedAt time.Time
 	ExpiresAt time.Time
@@ -23,6 +26,8 @@ type SnippetService struct {
 // Insert inserts a new SnippetModel into the database
 func (s *SnippetService) Insert(title, content string, expiresAt int) (int, error) {
 	slog.Debug(fmt.Sprintf("Inserting new snippet. Title: %s", title))
+	// Really don't prepare statements. There are a lot of gotcha's where they exist on the connection objects they were created. They can potentially
+	// recreate connections. It's an optimization you probably don't need at the moment.
 	stmt, err := s.DB.Prepare("INSERT INTO snippets (title, content, expires_at) VALUES ($1, $2, DATETIME(CURRENT_TIMESTAMP, '+' || $3 || ' DAY'))")
 	if err != nil {
 		slog.Debug("The prepared statement has an error")
@@ -37,7 +42,7 @@ func (s *SnippetService) Insert(title, content string, expiresAt int) (int, erro
 	// will hold on to a connection until .Close() is called.
 	res, err := stmt.Exec(title, content, expiresAt)
 	if err != nil {
-		slog.Debug("SQL DDL returned an error.")
+		slog.Debug("SQL DML statement returned an error.")
 		return 0, err
 	}
 
@@ -55,12 +60,88 @@ func (s *SnippetService) Insert(title, content string, expiresAt int) (int, erro
 	return int(lastId), nil
 }
 
-// Get retrieves a specific Snippet by ID
+// Get retrieves a specific Snippet by ID ignoring the record if expired.
 func (s *SnippetService) Get(id int) (Snippet, error) {
-	return Snippet{}, nil
+
+	stmt := `SELECT id, title, content, created_at, updated_at, expires_at FROM snippets 
+	WHERE expires_at > CURRENT_TIMESTAMP AND id = $1`
+
+	// errors from DB.QueryRow() are deferred until Scan() is called.
+	// meaning you could also have used DB.QueryRow(...).Scan(...)
+	row := s.DB.QueryRow(stmt, id)
+
+	var snip Snippet
+
+	err := row.Scan(&snip.ID,
+		&snip.Title,
+		&snip.Content,
+		&snip.CreatedAt,
+		&snip.UpdatedAt,
+		&snip.ExpiresAt,
+	)
+
+	if err != nil {
+		slog.Debug("SQL DML statement returned an error.")
+		// Loop up the difference between errors.Is and errors.As
+		if errors.Is(err, sql.ErrNoRows) {
+			return Snippet{}, ErrNoRecord
+		} else {
+			return Snippet{}, err
+		}
+	}
+
+	return snip, nil
 }
 
 // Latest retrieves up to latest 10 Snippets from the database.
-func (s *SnippetService) Lastest() (Snippet, error) {
-	return Snippet{}, nil
+func (s *SnippetService) Lastest() ([]Snippet, error) {
+
+	stmt := `SELECT id, title, content, created_at, updated_at, expires_at FROM snippets
+	WHERE expires_at > CURRENT_TIMESTAMP ORDER BY id DESC LIMIT 10`
+
+	rows, err := s.DB.Query(stmt)
+	if err != nil {
+		return nil, err
+	}
+
+	// We defer rows.Close() to ensure the sql.Rows resultset is
+	// always properly closed before the Latest() method returns. This defer
+	// statement should come *after* you check for an error from the Query()
+	// method. Otherwise, if Query() returns an error, you'll get a panic
+	// trying to close a nil resultset.
+	defer rows.Close()
+
+	var snippets []Snippet
+
+	// Use rows.Next to iterate through the rows in the resultset. This
+	// prepares the first (and then each subsequent) row to be acted on by the
+	// rows.Scan() method. If iteration over all the rows completes then the
+	// resultset automatically closes itself and frees-up the underlying
+	// database connection.
+	for rows.Next() {
+		var snip Snippet
+
+		err := rows.Scan(&snip.ID,
+			&snip.Title,
+			&snip.Content,
+			&snip.CreatedAt,
+			&snip.UpdatedAt,
+			&snip.ExpiresAt,
+		)
+		if err != nil {
+			return nil, err
+		}
+
+		snippets = append(snippets, snip)
+	}
+
+	// When the rows.Next() loop has finished we call rows.Err() to retrieve any
+	// error that was encountered during the iteration. It's important to
+	// call this - don't assume that a successful iteration was completed
+	// over the whole resultset.
+	if err = rows.Err(); err != nil {
+		return nil, err
+	}
+
+	return snippets, nil
 }

internal/server/base_server.go

@@ -2,8 +2,8 @@ package server
 
 import (
 	"database/sql"
+	"errors"
 	"fmt"
-	"html/template"
 	"log/slog"
 	"net/http"
 	"strconv"
@@ -55,29 +55,42 @@ func (rs *RatchetServer) home(w http.ResponseWriter, r *http.Request) {
 
 	w.Header().Add("Server", "Go")
 
-	// Initialize a slice containing the paths to the two files. It's important
-	// to note that the file containing our base template must be the *first*
-	// file in the slice.
-	files := []string{
-		"./ui/html/base.go.tmpl",
-		"./ui/html/partials/nav.go.tmpl",
-		"./ui/html/pages/home.go.tmpl",
-	}
-
-	// read template file into template set.
-	ts, err := template.ParseFiles(files...)
-	if err != nil {
+	// Retrieve Snippets from DB
+	snippets, err := rs.snippetService.Lastest()
+	if err != err {
 		rs.serverError(w, r, err)
 		return
 	}
-	// Write template content to response body
-	err = ts.ExecuteTemplate(w, "base", nil)
-	if err != nil {
-		// This is the older more verbose way of doing what RatchetServer.serverError does
-		// rs.logger.Error(err.Error())
-		// http.Error(w, "Internal Server Error", http.StatusInternalServerError)
-		rs.serverError(w, r, err)
+
+	rs.logger.Debug(fmt.Sprintf("%d snippets retrieved", len(snippets)))
+
+	for _, snippet := range snippets {
+		fmt.Fprintf(w, "%+v\n", snippet)
 	}
+
+	// // Initialize a slice containing the paths to the two files. It's important
+	// // to note that the file containing our base template must be the *first*
+	// // file in the slice.
+	// files := []string{
+	// 	"./ui/html/base.go.tmpl",
+	// 	"./ui/html/partials/nav.go.tmpl",
+	// 	"./ui/html/pages/home.go.tmpl",
+	// }
+
+	// // read template file into template set.
+	// ts, err := template.ParseFiles(files...)
+	// if err != nil {
+	// 	rs.serverError(w, r, err)
+	// 	return
+	// }
+	// // Write template content to response body
+	// err = ts.ExecuteTemplate(w, "base", nil)
+	// if err != nil {
+	// 	// This is the older more verbose way of doing what RatchetServer.serverError does
+	// 	// rs.logger.Error(err.Error())
+	// 	// http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+	// 	rs.serverError(w, r, err)
+	// }
 }
 
 func (rs *RatchetServer) snippetView(w http.ResponseWriter, r *http.Request) {
@@ -91,16 +104,21 @@ func (rs *RatchetServer) snippetView(w http.ResponseWriter, r *http.Request) {
 
 	// Set a new cache-control header. If an existing "Cache-Control" header exists
 	// it will be overwritten.
-	w.Header().Set("Cache-Control", "public, max-age=31536000")
-
-	// msg := fmt.Sprintf("Snippet %d...", id)
-
-	// w.Write([]byte(msg))
+	// w.Header().Set("Cache-Control", "public, max-age=31536000")
 
-	// we can rely on the Write() interface to use a differnent
-	// function to write out our response
+	snippet, err := rs.snippetService.Get(id)
+	if err != nil {
+		rs.logger.Debug(fmt.Sprintf("Failed to retrieve an active record with id: %d", id))
+		if errors.Is(err, model.ErrNoRecord) {
+			rs.clientError(w, http.StatusNotFound)
+		} else {
+			rs.serverError(w, r, err)
+		}
+		return
+	}
 
-	fmt.Fprintf(w, "Snippet %d...", id)
+	// Write the snippet data as a plain-text HTTP response body.
+	fmt.Fprintf(w, "%+v", snippet)
 }
 
 // snippetCreate handles display of the form used to create snippets