package collector

import (
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"log"
	"net/http"
	"strconv"
	"strings"
	"time"

	"git.tornberg.me/go-otel/internal/todos"
)

const (
	maxTodoBody = 16 << 10
	maxTodoText = 4000
	maxTodoMeta = 500
)

// SetTodoStore enables the todo endpoints.
func (c *Collector) SetTodoStore(s todos.Store) { c.todoStore = s }

func clipTo(s string, n int) string {
	s = strings.TrimSpace(s)
	if len(s) > n {
		return s[:n]
	}
	return s
}

type todoPayload struct {
	Project   string `json:"project"`
	Text      string `json:"text"`
	Component string `json:"component"`
	Path      string `json:"path"`
	Hash      string `json:"hash"`
	URL       string `json:"url"`
	UserAgent string `json:"ua"`
	Session   string `json:"session"`
}

// HandleTodoCreate ingests a todo posted by otel-todo.js. It is guarded by
// the same ingest key and rate limit as the other RUM endpoints.
func (c *Collector) HandleTodoCreate(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	if c.todoStore == nil {
		http.Error(w, "todos not enabled", http.StatusServiceUnavailable)
		return
	}
	if !c.checkIngest(w, r) {
		return
	}
	var p todoPayload
	if err := json.NewDecoder(http.MaxBytesReader(w, r.Body, maxTodoBody)).Decode(&p); err != nil {
		http.Error(w, "invalid todo payload", http.StatusBadRequest)
		return
	}
	text := clipTo(p.Text, maxTodoText)
	if text == "" {
		http.Error(w, "text is required", http.StatusBadRequest)
		return
	}
	project := clipTo(p.Project, maxTodoMeta)
	if project == "" {
		project = "frontend"
	}
	id := make([]byte, 8)
	_, _ = rand.Read(id)
	t := todos.Todo{
		ID:        hex.EncodeToString(id),
		Project:   project,
		Text:      text,
		Component: clipTo(p.Component, maxTodoMeta),
		Path:      clipTo(p.Path, maxTodoMeta),
		Hash:      clipTo(p.Hash, maxTodoMeta),
		URL:       clipTo(p.URL, maxTodoMeta),
		UserAgent: clipTo(p.UserAgent, maxTodoMeta),
		Session:   clipTo(p.Session, maxTodoMeta),
		CreatedAt: time.Now().UTC(),
	}
	if err := c.todoStore.Add(r.Context(), t); err != nil {
		log.Printf("failed to store todo: %v", err)
		http.Error(w, "failed to store todo", http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusCreated)
	_ = json.NewEncoder(w).Encode(t)
}

// HandleTodoList returns todos, newest first. ?project= filters by project
// (omit for all); ?limit= defaults to 100, max 1000. Registered behind auth.
func (c *Collector) HandleTodoList(w http.ResponseWriter, r *http.Request) {
	if c.todoStore == nil {
		http.Error(w, "todos not enabled", http.StatusServiceUnavailable)
		return
	}
	limit := 100
	if v, err := strconv.Atoi(r.URL.Query().Get("limit")); err == nil && v > 0 {
		limit = min(v, 1000)
	}
	items, err := c.todoStore.List(r.Context(), r.URL.Query().Get("project"), limit)
	if err != nil {
		log.Printf("failed to list todos: %v", err)
		http.Error(w, "failed to list todos", http.StatusInternalServerError)
		return
	}
	if items == nil {
		items = []todos.Todo{}
	}
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(items)
}