package main

import (
	"bufio"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"time"

	"git.tornberg.me/go-cart-actor/pkg/cart"
)

type FileServer struct {
	// Define fields here
	dataDir string
}

func NewFileServer(dataDir string) *FileServer {
	return &FileServer{
		dataDir: dataDir,
	}
}

func listCartFiles(dir string) ([]CartFileInfo, error) {
	entries, err := os.ReadDir(dir)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return []CartFileInfo{}, nil
		}
		return nil, err
	}
	out := make([]CartFileInfo, 0)
	for _, e := range entries {
		if e.IsDir() {
			continue
		}
		name := e.Name()
		var id uint64
		var parseErr error
		parts := strings.Split(name, ".")
		if len(parts) == 2 && parts[1] == "events.log" {
			idStr := parts[0]
			id, parseErr = strconv.ParseUint(idStr, 10, 64)
		} else if len(parts) == 3 && parts[1] == "events" && parts[2] == "log" {
			idStr := parts[0]
			id, parseErr = strconv.ParseUint(idStr, 10, 64)
		} else {
			continue
		}
		if parseErr != nil {
			continue
		}
		p := filepath.Join(dir, name)
		info, err := e.Info()
		if err != nil {
			continue
		}
		out = append(out, CartFileInfo{
			ID:       id,
			CartId:   cart.CartId(id),
			Path:     p,
			Size:     info.Size(),
			Modified: info.ModTime(),
		})
	}
	return out, nil
}

func readRawLogLines(path string) ([]string, error) {
	fh, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer fh.Close()
	lines := make([]string, 0, 64)
	s := bufio.NewScanner(fh)
	// increase buffer to handle larger JSON lines
	buf := make([]byte, 0, 1024*1024)
	s.Buffer(buf, 1024*1024)
	for s.Scan() {
		line := strings.TrimSpace(s.Text())
		if line == "" {
			continue
		}
		lines = append(lines, line)
	}
	if err := s.Err(); err != nil {
		return nil, err
	}
	return lines, nil
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Cache-Control", "no-cache")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(v)
}

func (fs *FileServer) CartsHandler(w http.ResponseWriter, r *http.Request) {
	list, err := listCartFiles(fs.dataDir)
	if err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}
	// sort by modified desc
	sort.Slice(list, func(i, j int) bool { return list[i].Modified.After(list[j].Modified) })
	carts := make([]map[string]any, 0, len(list))
	for _, it := range list {
		carts = append(carts, map[string]any{
			"id":       it.ID,
			"cartId":   cart.CartId(it.ID).String(),
			"filename": filepath.Base(it.Path),
			"path":     it.Path,
			"size":     it.Size,
			"modified": it.Modified,
		})
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"count": len(carts),
		"carts": carts,
	})
}

func (fs *FileServer) CartHandler(w http.ResponseWriter, r *http.Request) {
	idStr := r.PathValue("id")
	if idStr == "" {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "missing id"})
		return
	}

	id, err := strconv.ParseUint(idStr, 10, 64)
	if err != nil {
		if cartId, ok := cart.ParseCartId(idStr); !ok {
			writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid id"})
			return
		} else {
			id = uint64(cartId)
		}
	}
	// reconstruct state from event log if present
	grain := cart.NewCartGrain(id, time.Now())
	if globalDisk != nil {
		_ = globalDisk.LoadEvents(id, grain)
	}

	path := filepath.Join(fs.dataDir, fmt.Sprintf("%d.events.log", id))
	info, err := os.Stat(path)
	if err != nil && errors.Is(err, os.ErrNotExist) {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "cart not found"})
		return
	} else if err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}
	lines, err := readRawLogLines(path)
	if err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"id":     id,
		"cartId": cart.CartId(id).String(),
		"state":  grain,
		"rawLog": lines,
		"meta": map[string]any{
			"size":     info.Size(),
			"modified": info.ModTime(),
			"path":     path,
		},
	})
}