package handlers

import (
	"database/sql"
	"encoding/json"
	"net/http"
	"time"
)

type ReceiptHandler struct {
	DB *sql.DB
}

func NewReceiptHandler(db *sql.DB) *ReceiptHandler {
	return &ReceiptHandler{DB: db}
}

type Receipt struct {
	ID            string                 `json:"id"`
	EmployeeID    string                 `json:"employee_id"`
	ExpenseID     *string                `json:"expense_id"`
	ImageURL      string                 `json:"image_url"`
	OCRText       string                 `json:"ocr_text"`
	OCRData       map[string]interface{} `json:"ocr_data"`
	OCRConfidence float64                `json:"ocr_confidence"`
	Status        string                 `json:"status"`
	ProcessedAt   *time.Time             `json:"processed_at"`
	CreatedAt     time.Time              `json:"created_at"`
}

func (h *ReceiptHandler) ListReceipts(w http.ResponseWriter, r *http.Request) {
	status := r.URL.Query().Get("status")
	if status == "" {
		status = "all"
	}

	var query string
	var args []interface{}
	if status == "all" {
		query = `SELECT id, employee_id, expense_id, image_url, ocr_text, ocr_data, ocr_confidence, status, processed_at, created_at FROM boc_receipts ORDER BY created_at DESC LIMIT 100`
	} else {
		query = `SELECT id, employee_id, expense_id, image_url, ocr_text, ocr_data, ocr_confidence, status, processed_at, created_at FROM boc_receipts WHERE status = $1 ORDER BY created_at DESC LIMIT 100`
		args = append(args, status)
	}

	rows, err := h.DB.Query(query, args...)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "database error")
		return
	}
	defer rows.Close()

	receipts := []Receipt{}
	for rows.Next() {
		var rc Receipt
		var ocrData []byte
		if err := rows.Scan(&rc.ID, &rc.EmployeeID, &rc.ExpenseID, &rc.ImageURL, &rc.OCRText, &ocrData, &rc.OCRConfidence, &rc.Status, &rc.ProcessedAt, &rc.CreatedAt); err != nil {
			continue
		}
		json.Unmarshal(ocrData, &rc.OCRData)
		receipts = append(receipts, rc)
	}

	writeJSON(w, http.StatusOK, map[string]interface{}{
		"receipts": receipts,
		"total":    len(receipts),
	})
}

func (h *ReceiptHandler) UploadReceipt(w http.ResponseWriter, r *http.Request) {
	var req struct {
		EmployeeID string `json:"employee_id"`
		ImageURL   string `json:"image_url"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request")
		return
	}

	var id string
	err := h.DB.QueryRow(`
		INSERT INTO boc_receipts (employee_id, image_url, status)
		VALUES ($1, $2, 'pending')
		RETURNING id
	`, req.EmployeeID, req.ImageURL).Scan(&id)

	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to upload receipt")
		return
	}

	// TODO: Trigger async OCR processing
	go h.processOCR(id, req.ImageURL)

	writeJSON(w, http.StatusCreated, map[string]interface{}{
		"id":      id,
		"message": "Receipt uploaded, OCR processing started",
	})
}

func (h *ReceiptHandler) processOCR(receiptID, imageURL string) {
	// Placeholder for OCR processing
	// In production, this would call an OCR service (AWS Textract, Google Vision, etc.)

	// Simulate OCR processing
	time.Sleep(2 * time.Second)

	ocrData := map[string]interface{}{
		"amount":   125.50,
		"date":     time.Now().Format("2006-01-02"),
		"vendor":   "Example Store",
		"category": "Mat",
	}
	ocrJSON, _ := json.Marshal(ocrData)

	h.DB.Exec(`
		UPDATE boc_receipts
		SET ocr_text = $1, ocr_data = $2, ocr_confidence = $3, status = 'processed', processed_at = NOW()
		WHERE id = $4
	`, "Example Store\nDate: 2026-07-12\nTotal: $125.50", ocrJSON, 0.95, receiptID)
}

func (h *ReceiptHandler) ApproveReceipt(w http.ResponseWriter, r *http.Request) {
	var req struct {
		ReceiptID string  `json:"receipt_id"`
		Amount    float64 `json:"amount"`
		Category  string  `json:"category"`
		Description string `json:"description"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request")
		return
	}

	tx, err := h.DB.Begin()
	if err != nil {
		writeError(w, http.StatusInternalServerError, "transaction error")
		return
	}
	defer tx.Rollback()

	// Create expense from receipt
	var expenseID string
	err = tx.QueryRow(`
		INSERT INTO boc_expenses (category, description, amount, currency, status, receipt_url)
		VALUES ($1, $2, $3, 'USD', 'pending', (SELECT image_url FROM boc_receipts WHERE id = $4))
		RETURNING id
	`, req.Category, req.Description, req.Amount, req.ReceiptID).Scan(&expenseID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to create expense")
		return
	}

	// Link receipt to expense
	_, err = tx.Exec(`UPDATE boc_receipts SET expense_id = $1, status = 'approved' WHERE id = $2`, expenseID, req.ReceiptID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to update receipt")
		return
	}

	if err := tx.Commit(); err != nil {
		writeError(w, http.StatusInternalServerError, "commit failed")
		return
	}

	writeJSON(w, http.StatusOK, map[string]interface{}{
		"expense_id": expenseID,
		"message":    "Receipt approved and expense created",
	})
}