package handler

import (
	"errors"
	"strconv"

	"accounting-app/pkg/api"
	"accounting-app/internal/service"

	"github.com/gin-gonic/gin"
)

// RepaymentHandler handles HTTP requests for repayment plan operations
type RepaymentHandler struct {
	repaymentService *service.RepaymentService
}

// NewRepaymentHandler creates a new RepaymentHandler instance
func NewRepaymentHandler(repaymentService *service.RepaymentService) *RepaymentHandler {
	return &RepaymentHandler{
		repaymentService: repaymentService,
	}
}

// CreateRepaymentPlan handles POST /api/v1/repayment-plans
// Creates a new repayment plan for a bill
func (h *RepaymentHandler) CreateRepaymentPlan(c *gin.Context) {
	userId, exists := c.Get("user_id")
	if !exists {
		api.Unauthorized(c, "User not authenticated")
		return
	}

	var input service.CreateRepaymentPlanInput
	if err := c.ShouldBindJSON(&input); err != nil {
		api.ValidationError(c, "Invalid request body: "+err.Error())
		return
	}

	plan, err := h.repaymentService.CreateRepaymentPlan(userId.(uint), input)
	if err != nil {
		if errors.Is(err, service.ErrInvalidInstallmentCount) {
			api.BadRequest(c, "Installment count must be at least 2")
			return
		}
		if errors.Is(err, service.ErrBillAlreadyPaid) {
			api.BadRequest(c, "Bill is already paid")
			return
		}
		if errors.Is(err, service.ErrPlanAlreadyExists) {
			api.Conflict(c, "Repayment plan already exists for this bill")
			return
		}
		api.InternalError(c, "Failed to create repayment plan: "+err.Error())
		return
	}

	api.Created(c, plan)
}

// GetRepaymentPlan handles GET /api/v1/repayment-plans/:id
// Returns a repayment plan by ID
func (h *RepaymentHandler) GetRepaymentPlan(c *gin.Context) {
	userId, exists := c.Get("user_id")
	if !exists {
		api.Unauthorized(c, "User not authenticated")
		return
	}

	id, err := strconv.ParseUint(c.Param("id"), 10, 32)
	if err != nil {
		api.BadRequest(c, "Invalid plan ID")
		return
	}

	plan, err := h.repaymentService.GetRepaymentPlan(userId.(uint), uint(id))
	if err != nil {
		if errors.Is(err, service.ErrRepaymentPlanNotFound) {
			api.NotFound(c, "Repayment plan not found")
			return
		}
		api.InternalError(c, "Failed to get repayment plan: "+err.Error())
		return
	}

	api.Success(c, plan)
}

// GetActivePlans handles GET /api/v1/repayment-plans
// Returns all active repayment plans
func (h *RepaymentHandler) GetActivePlans(c *gin.Context) {
	userId, exists := c.Get("user_id")
	if !exists {
		api.Unauthorized(c, "User not authenticated")
		return
	}

	plans, err := h.repaymentService.GetActivePlans(userId.(uint))
	if err != nil {
		api.InternalError(c, "Failed to get active plans: "+err.Error())
		return
	}

	api.Success(c, plans)
}

// CancelRepaymentPlan handles DELETE /api/v1/repayment-plans/:id
// Cancels a repayment plan
func (h *RepaymentHandler) CancelRepaymentPlan(c *gin.Context) {
	userId, exists := c.Get("user_id")
	if !exists {
		api.Unauthorized(c, "User not authenticated")
		return
	}

	id, err := strconv.ParseUint(c.Param("id"), 10, 32)
	if err != nil {
		api.BadRequest(c, "Invalid plan ID")
		return
	}

	if err := h.repaymentService.CancelRepaymentPlan(userId.(uint), uint(id)); err != nil {
		if errors.Is(err, service.ErrRepaymentPlanNotFound) {
			api.NotFound(c, "Repayment plan not found")
			return
		}
		api.InternalError(c, "Failed to cancel repayment plan: "+err.Error())
		return
	}

	api.NoContent(c)
}

// GetDebtSummary handles GET /api/v1/debt-summary
// Returns a comprehensive debt summary
func (h *RepaymentHandler) GetDebtSummary(c *gin.Context) {
	userId, exists := c.Get("user_id")
	if !exists {
		api.Unauthorized(c, "User not authenticated")
		return
	}

	summary, err := h.repaymentService.GetDebtSummary(userId.(uint))
	if err != nil {
		api.InternalError(c, "Failed to get debt summary: "+err.Error())
		return
	}

	api.Success(c, summary)
}

// GetUnreadReminders handles GET /api/v1/payment-reminders
// Returns all unread payment reminders
func (h *RepaymentHandler) GetUnreadReminders(c *gin.Context) {
	userId, exists := c.Get("user_id")
	if !exists {
		api.Unauthorized(c, "User not authenticated")
		return
	}

	reminders, err := h.repaymentService.GetUnreadReminders(userId.(uint))
	if err != nil {
		api.InternalError(c, "Failed to get reminders: "+err.Error())
		return
	}

	api.Success(c, reminders)
}

// MarkReminderAsRead handles PUT /api/v1/payment-reminders/:id/read
// Marks a reminder as read
func (h *RepaymentHandler) MarkReminderAsRead(c *gin.Context) {
	id, err := strconv.ParseUint(c.Param("id"), 10, 32)
	if err != nil {
		api.BadRequest(c, "Invalid reminder ID")
		return
	}

	if err := h.repaymentService.MarkReminderAsRead(uint(id)); err != nil {
		api.InternalError(c, "Failed to mark reminder as read: "+err.Error())
		return
	}

	api.NoContent(c)
}

// RegisterRoutes registers repayment routes to the given router group
func (h *RepaymentHandler) RegisterRoutes(rg *gin.RouterGroup) {
	// Repayment plan routes
	plans := rg.Group("/repayment-plans")
	{
		plans.POST("", h.CreateRepaymentPlan)
		plans.GET("", h.GetActivePlans)
		plans.GET("/:id", h.GetRepaymentPlan)
		plans.DELETE("/:id", h.CancelRepaymentPlan)
	}

	// Debt summary route
	rg.GET("/debt-summary", h.GetDebtSummary)

	// Payment reminder routes
	reminders := rg.Group("/payment-reminders")
	{
		reminders.GET("", h.GetUnreadReminders)
		reminders.PUT("/:id/read", h.MarkReminderAsRead)
	}
}