package main

import (
	"cmp"
	"embed"
	"encoding/json"
	"errors"
	"fmt"
	"io/fs"
	"log"
	"net/http"
	"os"
	"regexp"
	"slices"
	"strings"
	"sync"
	"time"

	"github.com/a-h/templ"
	"gopkg.in/yaml.v3"
)

//go:embed public blogs
var embedded embed.FS

func Assert(ok bool) {
	if !ok {
		panic("assertion failure")
	}
}

type Theme struct {
	primary    string
	secondary  string
	accent     string
	extra      string
	text       string
	alt        string
	background string
}

type FontPack struct {
	Monospace string
	Normal    string
}

type Style struct {
	theme    Theme
	fontPack FontPack
}

var (
	mu        sync.RWMutex
	themes    = map[string]Theme{}
	fontPacks = map[string]FontPack{}
)

func SetFontPack(name string, fontPack FontPack) {
	mu.Lock()
	defer mu.Unlock()
	fontPacks[name] = fontPack
}

func GetFontPack(name string) (FontPack, bool) {
	mu.RLock()
	defer mu.RUnlock()
	fontPack, ok := fontPacks[name]
	return fontPack, ok
}

func SetTheme(name string, theme Theme) {
	mu.Lock()
	defer mu.Unlock()
	themes[name] = theme
}

func GetTheme(name string) (Theme, bool) {
	mu.RLock()
	defer mu.RUnlock()
	theme, ok := themes[name]
	return theme, ok
}

func currentStyle(r *http.Request) Style {
	theme, ok := GetTheme("default")
	Assert(ok)
	fontPack, ok := GetFontPack("default")
	Assert(ok)
	style := Style{
		theme:    theme,
		fontPack: fontPack,
	}

	if cookie, err := r.Cookie("theme"); err == nil {
		if theme, ok := GetTheme(cookie.Value); ok {
			style.theme = theme
		}
	}

	if cookie, err := r.Cookie("font-pack"); err == nil {
		if fontPack, ok := GetFontPack(cookie.Value); ok {
			style.fontPack = fontPack
		}
	}

	return style
}

func (theme Theme) Vars() map[string]string {
	return map[string]string{
		"primary":    theme.primary,
		"secondary":  theme.secondary,
		"accent":     theme.accent,
		"extra":      theme.extra,
		"text":       theme.text,
		"alt":        theme.alt,
		"background": theme.background,
	}
}

func (fontPack FontPack) Vars() map[string]string {
	return map[string]string{
		"font-mono":   fontPack.Monospace,
		"font-normal": fontPack.Normal,
	}
}

func (style Style) Vars() map[string]string {
	vars := style.theme.Vars()
	for k, v := range style.fontPack.Vars() {
		vars[k] = v
	}
	return vars
}

func styleToCss(style Style) templ.SafeCSS {
	var b strings.Builder
	for k, v := range style.Vars() {
		fmt.Fprintf(&b, "--%s:%s;", k, v)
	}
	return templ.SafeCSS(b.String())
}

type Blog struct {
	Slug  string
	Title string
	Desc  string
	Date  time.Time
	Body  string // raw markdown for rendering
}

type frontmatter struct {
	Title string    `yaml:"title"`
	Desc  string    `yaml:"description"`
	Date  time.Time `yaml:"date"`
}

var datePrefix = regexp.MustCompile(`^(\d{4}-\d{2}-\d{2})-(.+)\.md$`)

func parseBlog(name, raw string) (Blog, error) {
	raw = strings.ReplaceAll(raw, "\r\n", "\n")
	body := raw
	var frontmatter frontmatter
	if rest, ok := strings.CutPrefix(raw, "---\n"); ok {
		if head, after, found := strings.Cut(rest, "\n---\n"); found {
			if err := yaml.Unmarshal([]byte(head), &frontmatter); err != nil {
				return Blog{}, err
			}
			body = after
		}
	}

	slug := strings.TrimSuffix(name, ".md")
	date := frontmatter.Date // frontmatter wins
	if match := datePrefix.FindStringSubmatch(name); match != nil {
		slug = match[2]
		if date.IsZero() {
			date, _ = time.Parse(time.DateOnly, match[1])
		}
	}
	if date.IsZero() {
		return Blog{}, errors.New("no date in frontmatter or filename")
	}

	title := frontmatter.Title
	if title == "" {
		title = slug
	}
	return Blog{
		Slug:  slug,
		Title: title,
		Date:  date,
		Body:  body,
		Desc:  frontmatter.Desc,
	}, nil
}

func LoadBlogs(fsys fs.FS) ([]Blog, error) {
	entries, err := fs.ReadDir(fsys, ".")
	if err != nil {
		return nil, err
	}
	var blogs []Blog
	for _, e := range entries {
		if e.IsDir() || !strings.HasSuffix(e.Name(), ".md") || strings.HasPrefix(e.Name(), "_") {
			continue
		}
		raw, err := fs.ReadFile(fsys, e.Name())
		if err != nil {
			return nil, err
		}
		blog, err := parseBlog(e.Name(), string(raw))
		if err != nil {
			return nil, fmt.Errorf("%s: %w", e.Name(), err)
		}
		blogs = append(blogs, blog)
	}
	slices.SortFunc(blogs, func(a, b Blog) int { // newest first
		return cmp.Or(b.Date.Compare(a.Date), strings.Compare(a.Slug, b.Slug))
	})
	return blogs, nil
}

func loadBlogs() ([]Blog, error) {
	blogFS, err := fs.Sub(embedded, "blogs")
	if err != nil {
		return nil, err
	}
	return LoadBlogs(blogFS)
}

var (
	devMode     = os.Getenv("DEV") != ""
	cachedBlogs []Blog
)

func getBlogs() []Blog {
	if devMode || cachedBlogs == nil {
		var err error
		cachedBlogs, err = loadBlogs()
		if err != nil {
			log.Println("reloading blogs failed:", err)
		}
	}
	return cachedBlogs
}

func latestBlog(blogs []Blog) *Blog {
	if len(blogs) == 0 {
		return nil
	}
	return &blogs[0]
}

type Project struct {
	Name string
	Type string
	Desc []string
	Cmd  string
	Link string
}

var projects = []Project{
	{
		Name: "CPU vs AI",
		Type: "Game (made with Zig)",
		Desc: []string{
			"A tower defense game where an AI chip on your motherboard",
			"generates bugs! Place CPUs to destroy the bugs!",
			"Don't let them corrupt your RAM!",
		},
	},
	{
		Name: "Eko",
		Type: "Social Media Platform",
		Desc: []string{
			"A terminal-native alternative",
			"to Discord for Terminal",
			"nerds!",
		},
	},
	{
		Name: "Trident",
		Type: "IntelliJ Plugin",
		Desc: []string{
			"A blazingly fast way to",
			"Navigate to your mosta used",
			"files. Minimize keystrokes",
			"and maximize productivity!",
		},
	},
	{
		Name: "Dotfiles",
		Type: "Configuration",
		Desc: []string{
			"My Linux configuration,",
			"includes Neovim, tmux and",
			"other programs.",
		},
	},
}

func styleHandler(cookie string, lookup func(string) (map[string]string, bool)) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		name := r.PathValue("name")
		vars, ok := lookup(name)
		if !ok {
			http.NotFound(w, r)
			return
		}
		http.SetCookie(w, &http.Cookie{
			Name: cookie, Value: name, Path: "/",
			MaxAge: 31536000, SameSite: http.SameSiteLaxMode,
		})
		w.Header().Set("Cache-Control", "no-store")
		json.NewEncoder(w).Encode(vars)
	}
}

func notFoundHandler(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusNotFound)
	NotFoundPage(currentStyle(r), r.URL.Path).Render(r.Context(), w)
}

type MyUptime struct {
	mu         sync.RWMutex
	Uptime     string
	LastUpdate time.Time
}

var myUptime MyUptime

// GetMyUptime returns the current status string (handles offline state)
func GetMyUptime() string {
	myUptime.mu.RLock()
	defer myUptime.mu.RUnlock()

	// If no ping received in 3 minutes, treat as offline
	if time.Since(myUptime.LastUpdate) > 1*time.Minute {
		return "Asleep"
	}

	uptime := myUptime.Uptime
	uptime, _ = strings.CutPrefix(uptime, "up ")
	uptime = "Awake for " + uptime

	return uptime
}

func handleUptimePing(w http.ResponseWriter, r *http.Request) {
	if r.Method == http.MethodGet {
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(map[string]any{
			"uptime": GetMyUptime(),
		})
	} else if r.Method == http.MethodPost {
		if devMode == false {
			secretToken := os.Getenv("MY_UPTIME_TOKEN")
			if r.Header.Get("Authorization") != "Bearer "+secretToken {
				http.Error(w, "Unauthorized", http.StatusUnauthorized)
				return
			}
		}

		var req struct {
			Uptime string `json:"uptime"`
		}
		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
			http.Error(w, "Bad request", http.StatusBadRequest)
			return
		}

		myUptime.mu.Lock()
		myUptime.Uptime = req.Uptime
		myUptime.LastUpdate = time.Now()
		myUptime.mu.Unlock()

		w.WriteHeader(http.StatusOK)
	} else {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}
}

func main() {
	carbonightCat := Theme{
		primary:    "#94e2d5",
		// secondary:  "#b4befe",
		secondary:  "#BB91F0",
		accent:     "#74c7ec",
		extra:      "#a6e3a1",
		text:       "#cdd6f4",
		alt:        "#585b70",
		background: "#1e1e2e",
	}
	darkness := Theme{
		primary:    "#000000",
		secondary:  "#000000",
		accent:     "#000000",
		extra:      "#000000",
		text:       "#000000",
		alt:        "#000000",
		background: "#000000",
	}
	dark := Theme{
		primary:    "#54d7a9",
		secondary:  "#9b7eca",
		accent:     "#7ed4fb",
		extra:      "#8fcc75",
		text:       "#ffffff",
		alt:        "#999999",
		background: "#000000",
	}
	light := Theme{
		primary:    "#009399",
		secondary:  "#440b8e",
		accent:     "#177282",
		extra:      "#40a02b",
		text:       "#000000",
		alt:        "#4d4d4d",
		background: "#ffffff",
	}
	banana := Theme{
		primary:    "#ffdd44",
		secondary:  "#9b7eca",
		accent:     "#7ed4fb",
		extra:      "#000000",
		text:       "#ffffff",
		alt:        "#999999",
		background: "#000000",
	}

	jetbrains := FontPack{
		Monospace: "JetBrains Mono",
		Normal:    `system-ui, sans-serif`,
	}

	minecraft := FontPack{
		Monospace: `"Monocraft", "JetBrains Mono", monospace`,
		Normal:    `"Monocraft", system-ui, sans-serif`,
	}

	SetTheme("carbonight-cat", carbonightCat)
	SetTheme("banana", banana)
	SetTheme("black", dark)
	SetTheme("dark", darkness)

	SetTheme("light", light)
	SetTheme("white", light)
	SetTheme("sun", light)
	SetTheme("sunlight", light)
	SetTheme("flashbang", light)

	SetTheme("default", carbonightCat)

	SetFontPack("jetbrains", jetbrains)
	SetFontPack("minecraft", minecraft)
	SetFontPack("default", jetbrains)

	mux := http.NewServeMux()

	mux.Handle("GET /public/", http.FileServerFS(embedded))

	mux.HandleFunc("GET /api/my-uptime", handleUptimePing)
	mux.HandleFunc("POST /api/my-uptime", handleUptimePing)

	mux.HandleFunc("/", notFoundHandler) // matches everything
	mux.HandleFunc("GET /{$}", func(w http.ResponseWriter, r *http.Request) {
		HomePage(currentStyle(r), latestBlog(getBlogs())).Render(r.Context(), w)
	})

	mux.HandleFunc("GET /skills", func(w http.ResponseWriter, r *http.Request) {
		SkillsPage(currentStyle(r)).Render(r.Context(), w)
	})

	mux.HandleFunc("GET /projects", func(w http.ResponseWriter, r *http.Request) {
		ProjectsPage(currentStyle(r), projects).Render(r.Context(), w)
	})

	mux.HandleFunc("GET /blogs", func(w http.ResponseWriter, r *http.Request) {
		BlogsPage(currentStyle(r), getBlogs()).Render(r.Context(), w)
	})

	mux.HandleFunc("GET /theme/{name}", styleHandler("theme", func(n string) (map[string]string, bool) {
		theme, ok := GetTheme(n)
		return theme.Vars(), ok
	}))
	mux.HandleFunc("GET /font-pack/{name}", styleHandler("font-pack", func(n string) (map[string]string, bool) {
		fontPack, ok := GetFontPack(n)
		return fontPack.Vars(), ok
	}))

	fmt.Println("Server running at http://localhost:8080")
	if err := http.ListenAndServe(":8080", mux); err != nil {
		panic(err)
	}
}