package server

import (
	"fmt"
	"io"
	"net"
	"net/http"
	"os"
	"path/filepath"
	"time"

	"beelloo/internal/invoice"
	"beelloo/internal/render"
)

type Config struct {
	Addr    string
	MDPath  string
	CSSPath string
}

type Result struct {
	Listener net.Listener
}

func Serve(cfg Config, out, errOut io.Writer) error {
	if cfg.Addr == "" {
		cfg.Addr = "127.0.0.1:0"
	}
	cssPath, err := resolveCSSPath(cfg.MDPath, cfg.CSSPath)
	if err != nil {
		return err
	}
	cfg.CSSPath = cssPath

	listener, err := net.Listen("tcp", cfg.Addr)
	if err != nil {
		return fmt.Errorf("failed to listen on %s: %w", cfg.Addr, err)
	}

	mux := http.NewServeMux()
	mux.HandleFunc("/style.css", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Cache-Control", "no-store")
		w.Header().Set("Pragma", "no-cache")
		w.Header().Set("Expires", "0")
		if cfg.CSSPath != "" {
			http.ServeFile(w, r, cfg.CSSPath)
			return
		}
		css, err := render.DefaultCSS()
		if err != nil {
			http.Error(w, "failed to load default css", http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "text/css; charset=utf-8")
		_, _ = w.Write(css)
	})
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		file, err := os.Open(cfg.MDPath)
		if err != nil {
			http.Error(w, "failed to open markdown", http.StatusInternalServerError)
			return
		}
		defer file.Close()

		doc, err := invoice.ParseMarkdown(file)
		if err != nil {
			http.Error(w, "parse error: "+err.Error(), http.StatusBadRequest)
			return
		}
		if err := invoice.Validate(&doc); err != nil {
			http.Error(w, "validation error: "+err.Error(), http.StatusBadRequest)
			return
		}

		html, err := render.RenderHTMLWithCSSLink(doc, fmt.Sprintf("/style.css?v=%d", time.Now().UnixNano()))
		if err != nil {
			http.Error(w, "render error: "+err.Error(), http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		_, _ = w.Write([]byte(html))
	})

	server := &http.Server{Handler: mux}
	if cfg.CSSPath != "" {
		fmt.Fprintf(out, "Using CSS: %s\n", cfg.CSSPath)
	} else {
		fmt.Fprintln(out, "Using embedded CSS")
	}
	fmt.Fprintf(out, "Serving on http://%s/\n", listener.Addr().String())
	if err := server.Serve(listener); err != nil && err != http.ErrServerClosed {
		return fmt.Errorf("server error: %w", err)
	}
	return nil
}

func resolveCSSPath(mdPath, override string) (string, error) {
	if override != "" {
		if _, err := os.Stat(override); err != nil {
			return "", fmt.Errorf("failed to stat css file %s: %w", override, err)
		}
		return override, nil
	}
	if mdPath == "" {
		return "", nil
	}
	mdDir := filepath.Dir(mdPath)
	candidates := []string{
		filepath.Join(mdDir, "style.css"),
		"style.css",
	}
	for _, path := range candidates {
		if _, err := os.Stat(path); err == nil {
			return path, nil
		}
	}
	return "", nil
}