package main

import (
    "html/template" // New import
    "path/filepath" // New import

    "snippetbox.letsgofa.net/internal/models"
)

...

func newTemplateCache() (map[string]*template.Template, error) {
    // Initialize a new map to act as the cache.
    cache := map[string]*template.Template{}

    // Use the filepath.Glob() function to get a slice of all filepaths that
    // match the pattern "./ui/html/pages/*.tmpl". This will essentially gives
    // us a slice of all the filepaths for our application 'page' templates
    // like: [ui/html/pages/home.tmpl ui/html/pages/view.tmpl]
    pages, err := filepath.Glob("./ui/html/pages/*.tmpl")
    if err != nil {
        return nil, err
    }

    // Loop through the page filepaths one-by-one.
    for _, page := range pages {
        // Extract the file name (like 'home.tmpl') from the full filepath
        // and assign it to the name variable.
        name := filepath.Base(page)

        // Create a slice containing the filepaths for our base template, any
        // partials and the page.
        files := []string{
            "./ui/html/base.tmpl",
            "./ui/html/partials/nav.tmpl",
            page,
        }

        // Parse the files into a template set.
        ts, err := template.ParseFiles(files...)
        if err != nil {
            return nil, err
        }

        // Add the template set to the map, using the name of the page
        // (like 'home.tmpl') as the key.
        cache[name] = ts
    }

    // Return the map.
    return cache, nil
}

package main

import (
    "database/sql"
    "flag"
    "html/template" // New import
    "log/slog"
    "net/http"
    "os"

    "snippetbox.letsgofa.net/internal/models"

    _ "github.com/go-sql-driver/mysql"
)

// Add a templateCache field to the application struct.
type application struct {
    logger        *slog.Logger
    snippets      *models.SnippetModel
    templateCache map[string]*template.Template
}

func main() {
    addr := flag.String("addr", ":4000", "HTTP network address")
    dsn := flag.String("dsn", "web:pass@/snippetbox?parseTime=true", "MySQL data source name")
    flag.Parse()

    logger := slog.New(slog.NewTextHandler(os.Stdout, nil))

    db, err := openDB(*dsn)
    if err != nil {
        logger.Error(err.Error())
        os.Exit(1)
    }
    defer db.Close()

    // Initialize a new template cache...
    templateCache, err := newTemplateCache()
    if err != nil {
        logger.Error(err.Error())
        os.Exit(1)
    }

    // And add it to the application dependencies.
    app := &application{
        logger:        logger,
        snippets:      &models.SnippetModel{DB: db},
        templateCache: templateCache,
    }

    logger.Info("starting server", "addr", *addr)

    err = http.ListenAndServe(*addr, app.routes())
    logger.Error(err.Error())
    os.Exit(1)
}

...

package main

import (
    "fmt" // New import
    "net/http"
)

...

func (app *application) render(w http.ResponseWriter, r *http.Request, status int, page string, data templateData) {
    // Retrieve the appropriate template set from the cache based on the page
    // name (like 'home.tmpl'). If no entry exists in the cache with the
    // provided name, then create a new error and call the serverError() helper
    // method that we made earlier and return.
    ts, ok := app.templateCache[page]
    if !ok {
        err := fmt.Errorf("the template %s does not exist", page)
        app.serverError(w, r, err)
        return
    }

    // Write out the provided HTTP status code ('200 OK', '400 Bad Request' etc).
    w.WriteHeader(status)

    // Execute the template set and write the response body. Again, if there
    // is any error we call the serverError() helper.
    err := ts.ExecuteTemplate(w, "base", data)
    if err != nil {
        app.serverError(w, r, err)
    }
}

package main

import (
    "errors"
    "fmt"
    "net/http"
    "strconv"

    "snippetbox.letsgofa.net/internal/models"
)

func (app *application) home(w http.ResponseWriter, r *http.Request) {
    w.Header().Add("Server", "Go")
    
    snippets, err := app.snippets.Latest()
    if err != nil {
        app.serverError(w, r, err)
        return
    }

    // Use the new render helper.
    app.render(w, r, http.StatusOK, "home.tmpl", templateData{
        Snippets: snippets,
    })
}

func (app *application) snippetView(w http.ResponseWriter, r *http.Request) {
    id, err := strconv.Atoi(r.PathValue("id"))
    if err != nil || id < 1 {
        http.NotFound(w, r)
        return
    }

    snippet, err := app.snippets.Get(id)
    if err != nil {
        if errors.Is(err, models.ErrNoRecord) {
            http.NotFound(w, r)
        } else {
            app.serverError(w, r, err)
        }
        return
    }

    // Use the new render helper.
    app.render(w, r, http.StatusOK, "view.tmpl", templateData{
        Snippet: snippet,
    })
}

...