package handlers

import (
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
	"time"

	"git.jnss.me/joakim/opal/internal/engine"
	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"
)

// Response helpers (avoiding import cycle)
func jsonResponse(w http.ResponseWriter, status int, data interface{}) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(map[string]interface{}{
		"success": status >= 200 && status < 300,
		"data":    data,
	})
}

func errorResponse(w http.ResponseWriter, status int, message string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(map[string]interface{}{
		"success": false,
		"error":   message,
	})
}

// ListTasks returns tasks based on filter query parameters or a named report
func ListTasks(w http.ResponseWriter, r *http.Request) {
	query := r.URL.Query()

	// Check for report mode
	if reportName := query.Get("report"); reportName != "" {
		report, err := engine.GetReport(reportName)
		if err != nil {
			errorResponse(w, http.StatusBadRequest, err.Error())
			return
		}

		tasks, err := report.Execute(nil)
		if err != nil {
			errorResponse(w, http.StatusInternalServerError, err.Error())
			return
		}

		// Report sorts may already populate urgency, but ensure it for all paths
		engine.PopulateUrgency(tasks...)

		jsonResponse(w, http.StatusOK, map[string]interface{}{
			"report": reportName,
			"tasks":  tasks,
			"count":  len(tasks),
		})
		return
	}

	// Build filter from query params
	filter := engine.NewFilter()

	// Status filter
	if status := query.Get("status"); status != "" {
		filter.Attributes["status"] = status
	}

	// Project filter
	if project := query.Get("project"); project != "" {
		filter.Attributes["project"] = project
	}

	// Priority filter
	if priority := query.Get("priority"); priority != "" {
		filter.Attributes["priority"] = priority
	}

	// Tag filters
	if tags := query["tag"]; len(tags) > 0 {
		filter.IncludeTags = tags
	}

	// Get tasks
	tasks, err := engine.GetTasks(filter)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, err.Error())
		return
	}

	engine.PopulateUrgency(tasks...)
	jsonResponse(w, http.StatusOK, tasks)
}

// CreateTaskRequest represents the request body for creating a task
type CreateTaskRequest struct {
	Description string   `json:"description"`
	Tags        []string `json:"tags,omitempty"`
	Project     *string  `json:"project,omitempty"`
	Priority    *string  `json:"priority,omitempty"`
	Due         *int64   `json:"due,omitempty"`
	Scheduled   *int64   `json:"scheduled,omitempty"`
	Wait        *int64   `json:"wait,omitempty"`
	Until       *int64   `json:"until,omitempty"`
	Recurrence  *string  `json:"recurrence,omitempty"`
}

// CreateTask creates a new task
func CreateTask(w http.ResponseWriter, r *http.Request) {
	var req CreateTaskRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid request body")
		return
	}

	if req.Description == "" {
		errorResponse(w, http.StatusBadRequest, "description is required")
		return
	}

	// Build modifier from request
	mod := engine.NewModifier()
	mod.AddTags = req.Tags

	if req.Project != nil {
		mod.SetAttributes["project"] = req.Project
	}

	if req.Priority != nil {
		mod.SetAttributes["priority"] = req.Priority
	}

	if req.Due != nil {
		dueStr := fmt.Sprintf("%d", *req.Due)
		mod.SetAttributes["due"] = &dueStr
	}

	if req.Scheduled != nil {
		scheduledStr := fmt.Sprintf("%d", *req.Scheduled)
		mod.SetAttributes["scheduled"] = &scheduledStr
	}

	if req.Wait != nil {
		waitStr := fmt.Sprintf("%d", *req.Wait)
		mod.SetAttributes["wait"] = &waitStr
	}

	if req.Until != nil {
		untilStr := fmt.Sprintf("%d", *req.Until)
		mod.SetAttributes["until"] = &untilStr
	}

	if req.Recurrence != nil {
		mod.SetAttributes["recurrence"] = req.Recurrence
	}

	// Create task
	task, err := engine.CreateTaskWithModifier(req.Description, mod)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, err.Error())
		return
	}

	engine.PopulateUrgency(task)
	jsonResponse(w, http.StatusCreated, task)
}

// GetTask returns a single task by UUID
func GetTask(w http.ResponseWriter, r *http.Request) {
	uuidStr := chi.URLParam(r, "uuid")

	taskUUID, err := uuid.Parse(uuidStr)
	if err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid UUID")
		return
	}

	task, err := engine.GetTask(taskUUID)
	if err != nil {
		errorResponse(w, http.StatusNotFound, "task not found")
		return
	}

	engine.PopulateUrgency(task)
	jsonResponse(w, http.StatusOK, task)
}

// UpdateTaskRequest represents the request body for updating a task
type UpdateTaskRequest struct {
	Description *string `json:"description,omitempty"`
	Status      *string `json:"status,omitempty"`
	Priority    *string `json:"priority,omitempty"`
	Project     *string `json:"project,omitempty"`
	Due         *int64  `json:"due,omitempty"`
	Scheduled   *int64  `json:"scheduled,omitempty"`
	Wait        *int64  `json:"wait,omitempty"`
	Until       *int64  `json:"until,omitempty"`
	Start       *int64  `json:"start,omitempty"`
	Recurrence  *string `json:"recurrence,omitempty"`
}

// UpdateTask updates an existing task
func UpdateTask(w http.ResponseWriter, r *http.Request) {
	uuidStr := chi.URLParam(r, "uuid")

	taskUUID, err := uuid.Parse(uuidStr)
	if err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid UUID")
		return
	}

	task, err := engine.GetTask(taskUUID)
	if err != nil {
		errorResponse(w, http.StatusNotFound, "task not found")
		return
	}

	var req UpdateTaskRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid request body")
		return
	}

	// Build modifier
	mod := engine.NewModifier()

	if req.Description != nil {
		mod.SetAttributes["description"] = req.Description
	}

	if req.Status != nil {
		mod.SetAttributes["status"] = req.Status
	}

	if req.Priority != nil {
		mod.SetAttributes["priority"] = req.Priority
	}

	if req.Project != nil {
		mod.SetAttributes["project"] = req.Project
	}

	if req.Due != nil {
		dueStr := fmt.Sprintf("%d", *req.Due)
		mod.SetAttributes["due"] = &dueStr
	}

	if req.Scheduled != nil {
		scheduledStr := fmt.Sprintf("%d", *req.Scheduled)
		mod.SetAttributes["scheduled"] = &scheduledStr
	}

	if req.Wait != nil {
		waitStr := fmt.Sprintf("%d", *req.Wait)
		mod.SetAttributes["wait"] = &waitStr
	}

	if req.Until != nil {
		untilStr := fmt.Sprintf("%d", *req.Until)
		mod.SetAttributes["until"] = &untilStr
	}

	if req.Start != nil {
		t := time.Unix(*req.Start, 0)
		task.Start = &t
	}

	if req.Recurrence != nil {
		mod.SetAttributes["recurrence"] = req.Recurrence
	}

	// Apply modifier
	if err := mod.Apply(task); err != nil {
		errorResponse(w, http.StatusBadRequest, err.Error())
		return
	}

	engine.PopulateUrgency(task)
	jsonResponse(w, http.StatusOK, task)
}

// DeleteTask deletes a task
func DeleteTask(w http.ResponseWriter, r *http.Request) {
	uuidStr := chi.URLParam(r, "uuid")

	taskUUID, err := uuid.Parse(uuidStr)
	if err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid UUID")
		return
	}

	task, err := engine.GetTask(taskUUID)
	if err != nil {
		errorResponse(w, http.StatusNotFound, "task not found")
		return
	}

	// Check for permanent delete flag
	permanent := r.URL.Query().Get("permanent") == "true"

	if err := task.Delete(permanent); err != nil {
		errorResponse(w, http.StatusInternalServerError, err.Error())
		return
	}

	jsonResponse(w, http.StatusOK, map[string]string{"message": "task deleted"})
}

// CompleteTask marks a task as completed
func CompleteTask(w http.ResponseWriter, r *http.Request) {
	uuidStr := chi.URLParam(r, "uuid")

	taskUUID, err := uuid.Parse(uuidStr)
	if err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid UUID")
		return
	}

	task, err := engine.GetTask(taskUUID)
	if err != nil {
		errorResponse(w, http.StatusNotFound, "task not found")
		return
	}

	if err := task.Complete(); err != nil {
		errorResponse(w, http.StatusInternalServerError, err.Error())
		return
	}

	engine.PopulateUrgency(task)
	jsonResponse(w, http.StatusOK, task)
}

// StartTask sets the start time for a task
func StartTask(w http.ResponseWriter, r *http.Request) {
	uuidStr := chi.URLParam(r, "uuid")

	taskUUID, err := uuid.Parse(uuidStr)
	if err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid UUID")
		return
	}

	task, err := engine.GetTask(taskUUID)
	if err != nil {
		errorResponse(w, http.StatusNotFound, "task not found")
		return
	}

	if err := task.StartTask(); err != nil {
		errorResponse(w, http.StatusInternalServerError, err.Error())
		return
	}

	engine.PopulateUrgency(task)
	jsonResponse(w, http.StatusOK, task)
}

// StopTask clears the start time for a task
func StopTask(w http.ResponseWriter, r *http.Request) {
	uuidStr := chi.URLParam(r, "uuid")

	taskUUID, err := uuid.Parse(uuidStr)
	if err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid UUID")
		return
	}

	task, err := engine.GetTask(taskUUID)
	if err != nil {
		errorResponse(w, http.StatusNotFound, "task not found")
		return
	}

	if err := task.StopTask(); err != nil {
		errorResponse(w, http.StatusInternalServerError, err.Error())
		return
	}

	engine.PopulateUrgency(task)
	jsonResponse(w, http.StatusOK, task)
}

// GetTaskTags returns all tags for a task
func GetTaskTags(w http.ResponseWriter, r *http.Request) {
	uuidStr := chi.URLParam(r, "uuid")

	taskUUID, err := uuid.Parse(uuidStr)
	if err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid UUID")
		return
	}

	task, err := engine.GetTask(taskUUID)
	if err != nil {
		errorResponse(w, http.StatusNotFound, "task not found")
		return
	}

	jsonResponse(w, http.StatusOK, task.Tags)
}

// AddTaskTagRequest represents the request to add a tag
type AddTaskTagRequest struct {
	Tag string `json:"tag"`
}

// AddTaskTag adds a tag to a task
func AddTaskTag(w http.ResponseWriter, r *http.Request) {
	uuidStr := chi.URLParam(r, "uuid")

	taskUUID, err := uuid.Parse(uuidStr)
	if err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid UUID")
		return
	}

	task, err := engine.GetTask(taskUUID)
	if err != nil {
		errorResponse(w, http.StatusNotFound, "task not found")
		return
	}

	var req AddTaskTagRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid request body")
		return
	}

	if req.Tag == "" {
		errorResponse(w, http.StatusBadRequest, "tag is required")
		return
	}

	if err := task.AddTag(req.Tag); err != nil {
		errorResponse(w, http.StatusInternalServerError, err.Error())
		return
	}

	engine.PopulateUrgency(task)
	jsonResponse(w, http.StatusOK, task)
}

// ParseTaskRequest represents the request body for parsing a CLI-style task input
type ParseTaskRequest struct {
	Input string `json:"input"`
}

// ParseTask accepts a raw CLI-style input string, parses it, and creates a task
func ParseTask(w http.ResponseWriter, r *http.Request) {
	var req ParseTaskRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid request body")
		return
	}

	input := strings.TrimSpace(req.Input)
	if input == "" {
		errorResponse(w, http.StatusBadRequest, "input is required")
		return
	}

	// Split input on whitespace
	args := strings.Fields(input)

	// Classify args: words with +/- prefix or containing : are modifiers
	var descParts []string
	var modifierArgs []string
	for _, arg := range args {
		if strings.HasPrefix(arg, "+") || strings.HasPrefix(arg, "-") || strings.Contains(arg, ":") {
			modifierArgs = append(modifierArgs, arg)
		} else {
			descParts = append(descParts, arg)
		}
	}

	if len(descParts) == 0 {
		errorResponse(w, http.StatusBadRequest, "description is required")
		return
	}
	description := strings.Join(descParts, " ")

	// Parse modifiers
	var mod *engine.Modifier
	if len(modifierArgs) > 0 {
		var err error
		mod, err = engine.ParseModifier(modifierArgs)
		if err != nil {
			errorResponse(w, http.StatusBadRequest, fmt.Sprintf("failed to parse modifiers: %v", err))
			return
		}
	}

	// Check for recurring task
	if mod != nil && mod.SetAttributes["recur"] != nil {
		instance, err := engine.CreateRecurringTask(description, mod)
		if err != nil {
			errorResponse(w, http.StatusBadRequest, err.Error())
			return
		}
		engine.PopulateUrgency(instance)
		jsonResponse(w, http.StatusCreated, map[string]interface{}{"task": instance})
		return
	}

	// Create regular task
	task, err := engine.CreateTaskWithModifier(description, mod)
	if err != nil {
		errorResponse(w, http.StatusBadRequest, err.Error())
		return
	}

	engine.PopulateUrgency(task)
	jsonResponse(w, http.StatusCreated, map[string]interface{}{"task": task})
}

// RemoveTaskTag removes a tag from a task
func RemoveTaskTag(w http.ResponseWriter, r *http.Request) {
	uuidStr := chi.URLParam(r, "uuid")
	tag := chi.URLParam(r, "tag")

	taskUUID, err := uuid.Parse(uuidStr)
	if err != nil {
		errorResponse(w, http.StatusBadRequest, "invalid UUID")
		return
	}

	task, err := engine.GetTask(taskUUID)
	if err != nil {
		errorResponse(w, http.StatusNotFound, "task not found")
		return
	}

	if err := task.RemoveTag(tag); err != nil {
		errorResponse(w, http.StatusInternalServerError, err.Error())
		return
	}

	engine.PopulateUrgency(task)
	jsonResponse(w, http.StatusOK, task)
}