implement live-reloading dev server

Squashed commit of the following:

commit 02f077432202af4d633eb2cad81dfdaa6921317f
Author: Alan Pearce <alan@alanpearce.eu>
Date:   Sat Apr 27 21:09:14 2024 +0200

    builder: only remove output directory if set and in dev mode

commit 47001e01c55fa6e74aafeda04ebc3e4e7c47eba0
Author: Alan Pearce <alan@alanpearce.eu>
Date:   Sat Apr 27 21:03:37 2024 +0200

    implement live reload on dev server

commit 411ec969f61e4b73439f1c54ea29f75135ecc618
Author: Alan Pearce <alan@alanpearce.eu>
Date:   Sat Apr 27 20:59:26 2024 +0200

    server: implement graceful shutdown

commit 5400132eb6eb1b638e0b3fd4265f51611c92d473
Author: Alan Pearce <alan@alanpearce.eu>
Date:   Sat Apr 27 20:41:07 2024 +0200

    add some debug logs

commit 3c9b678197c044603950232d222f501ef74d7873
Author: Alan Pearce <alan@alanpearce.eu>
Date:   Sat Apr 27 20:39:09 2024 +0200

    prefix log output with executable name

commit 300e24c179e390e9d3f5aeab4471c97f17f1fa64
Author: Alan Pearce <alan@alanpearce.eu>
Date:   Sat Apr 27 20:29:42 2024 +0200

    don't panic inside internal packages, return error instead

commit fe2715d330402ad67fe866471bed89c7238ad2ec
Author: Alan Pearce <alan@alanpearce.eu>
Date:   Fri Apr 26 01:18:29 2024 +0200

    config: use a table to configure CSP headers

commit d012553aaf78a436fa8871830b5d720a9e292d4b
Author: Alan Pearce <alan@alanpearce.eu>
Date:   Thu Apr 25 17:13:39 2024 +0200

    dev: create basic dev server to build and serve from a temporary directory

commit a1d11d3e69650d9b43ca1b1d7b7ccc05a808d5c1
Author: Alan Pearce <alan@alanpearce.eu>
Date:   Thu Apr 25 13:02:22 2024 +0200

    remove unused redirect_other_hostnames config option

commit fd67b19b5c7f76f0c3579e8a05ef20a618e90be7
Author: Alan Pearce <alan@alanpearce.eu>
Date:   Thu Apr 25 12:58:53 2024 +0200

    server: make port a string, which is what go uses

commit c798e8e736c0649008cade337158399470a9099b
Author: Alan Pearce <alan@alanpearce.eu>
Date:   Thu Apr 25 12:58:33 2024 +0200

    config: remove unused port variable

commit f94882b9001f3b0855e26b26b4a84b96e3deb22b
Author: Alan Pearce <alan@alanpearce.eu>
Date:   Thu Apr 25 12:49:10 2024 +0200

    re-organise module layout

1 files changed, 0 insertions, 196 deletions

diff --git a/cmd/build/build.go b/cmd/build/build.go
deleted file mode 100644
index 5daa940..0000000
--- a/cmd/build/build.go
+++ /dev/null
@@ -1,196 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"io"
-	"log"
-	"log/slog"
-	"net/url"
-	"os"
-	"path"
-	"slices"
-
-	"website/internal/config"
-
-	cp "github.com/otiai10/copy"
-	"github.com/pkg/errors"
-)
-
-func mkdirp(dirs ...string) error {
-	return os.MkdirAll(path.Join(dirs...), 0755)
-}
-
-func outputToFile(output io.Reader, filename ...string) error {
-	file, err := os.OpenFile(path.Join(filename...), os.O_WRONLY|os.O_CREATE, 0644)
-	if err != nil {
-		return errors.WithMessage(err, "could not open output file")
-	}
-	defer file.Close()
-
-	if _, err := file.ReadFrom(output); err != nil {
-		return errors.WithMessage(err, "could not write output file")
-	}
-	return nil
-}
-
-func build(outDir string, config config.Config) error {
-	privateDir := path.Join(outDir, "private")
-	if err := mkdirp(privateDir); err != nil {
-		return errors.WithMessage(err, "could not create private directory")
-	}
-	publicDir := path.Join(outDir, "public")
-	if err := mkdirp(publicDir); err != nil {
-		return errors.WithMessage(err, "could not create public directory")
-	}
-
-	err := cp.Copy("static", publicDir, cp.Options{
-		PreserveTimes:     true,
-		PermissionControl: cp.AddPermission(0755),
-	})
-	if err != nil {
-		log.Panic(errors.Errorf("could not copy static files: %v", err))
-	}
-
-	if err := mkdirp(publicDir, "post"); err != nil {
-		return errors.WithMessage(err, "could not create post output directory")
-	}
-	slog.Debug("reading posts")
-	posts, tags, err := readPosts("content", "post", publicDir)
-	if err != nil {
-		return err
-	}
-
-	for _, post := range posts {
-		if err := mkdirp(publicDir, "post", post.Basename); err != nil {
-			return errors.WithMessage(err, "could not create directory for post")
-		}
-		slog.Debug("rendering post", "post", post.Basename)
-		output, err := renderPost(post, config)
-		if err != nil {
-			return errors.WithMessagef(err, "could not render post %s", post.Input)
-		}
-		if err := outputToFile(output, post.Output); err != nil {
-			return err
-		}
-	}
-
-	if err := mkdirp(publicDir, "tags"); err != nil {
-		return errors.WithMessage(err, "could not create directory for tags")
-	}
-	slog.Debug("rendering tags list")
-	output, err := renderTags(tags, config, "/tags")
-	if err != nil {
-		return errors.WithMessage(err, "could not render tags")
-	}
-	if err := outputToFile(output, publicDir, "tags", "index.html"); err != nil {
-		return err
-	}
-
-	for _, tag := range tags.ToSlice() {
-		matchingPosts := []Post{}
-		for _, post := range posts {
-			if slices.Contains(post.Taxonomies.Tags, tag) {
-				matchingPosts = append(matchingPosts, post)
-			}
-		}
-		if err := mkdirp(publicDir, "tags", tag); err != nil {
-			return errors.WithMessage(err, "could not create directory")
-		}
-		slog.Debug("rendering tags page", "tag", tag)
-		output, err := renderListPage(tag, config, matchingPosts, "/tags/"+tag)
-		if err != nil {
-			return errors.WithMessage(err, "could not render tag page")
-		}
-		if err := outputToFile(output, publicDir, "tags", tag, "index.html"); err != nil {
-			return err
-		}
-
-		slog.Debug("rendering tags feed", "tag", tag)
-		output, err = renderFeed(fmt.Sprintf("%s - %s", config.Title, tag), config, matchingPosts, tag)
-		if err != nil {
-			return errors.WithMessage(err, "could not render tag feed page")
-		}
-		if err := outputToFile(output, publicDir, "tags", tag, "atom.xml"); err != nil {
-			return err
-		}
-	}
-
-	slog.Debug("rendering list page")
-	listPage, err := renderListPage("", config, posts, "/post")
-	if err != nil {
-		return errors.WithMessage(err, "could not render list page")
-	}
-	if err := outputToFile(listPage, publicDir, "post", "index.html"); err != nil {
-		return err
-	}
-
-	slog.Debug("rendering feed")
-	feed, err := renderFeed(config.Title, config, posts, "feed")
-	if err != nil {
-		return errors.WithMessage(err, "could not render feed")
-	}
-	if err := outputToFile(feed, publicDir, "atom.xml"); err != nil {
-		return err
-	}
-
-	slog.Debug("rendering feed styles")
-	feedStyles, err := renderFeedStyles()
-	if err != nil {
-		return errors.WithMessage(err, "could not render feed styles")
-	}
-	if err := outputToFile(feedStyles, publicDir, "feed-styles.xsl"); err != nil {
-		return err
-	}
-
-	slog.Debug("rendering homepage")
-	homePage, err := renderHomepage(config, posts, "/")
-	if err != nil {
-		return errors.WithMessage(err, "could not render homepage")
-	}
-	if err := outputToFile(homePage, publicDir, "index.html"); err != nil {
-		return err
-	}
-
-	slog.Debug("rendering 404 page")
-	notFound, err := render404(config, "/404.html")
-	if err != nil {
-		return errors.WithMessage(err, "could not render 404 page")
-	}
-	if err := outputToFile(notFound, privateDir, "404.html"); err != nil {
-		return err
-	}
-
-	return nil
-}
-
-type IOConfig struct {
-	Source      string `conf:"default:.,short:s"`
-	Destination string `conf:"default:website,short:d"`
-	BaseURL     config.URL
-}
-
-func buildSite(ioConfig IOConfig) error {
-	config, err := config.GetConfig()
-	if err != nil {
-		log.Panic(errors.Errorf("could not get config: %v", err))
-	}
-
-	if ioConfig.BaseURL.URL != nil {
-		config.BaseURL.URL, err = url.Parse(ioConfig.BaseURL.String())
-		if err != nil {
-			log.Panic(errors.Errorf("highly unlikely: %v", err))
-		}
-	}
-
-	err = os.RemoveAll(ioConfig.Destination)
-	if err != nil {
-		log.Panic(errors.Errorf("could not remove public directory: %v", err))
-	}
-
-	if err := build(ioConfig.Destination, *config); err != nil {
-		return err
-	}
-
-	slog.Debug("done")
-	return nil
-}