package checker

import (
	"sync"
	"time"

	"github.com/intodns/backend/internal/resolver"
)

// Checker orchestrates all DNS health checks for a domain.
type Checker struct {
	resolver *resolver.Resolver
}

// NewChecker creates a Checker with a default Resolver.
func NewChecker() *Checker {
	return &Checker{
		resolver: resolver.NewResolver(),
	}
}

// StreamEvent is sent for each completed category during streaming.
type StreamEvent struct {
	Domain   string   `json:"domain,omitempty"`
	Category Category `json:"category"`
	Done     bool     `json:"done,omitempty"`
}

// Check runs all category checks in parallel and returns a Report.
func (c *Checker) Check(domain string) *Report {
	start := time.Now()

	type catResult struct {
		index int
		cat   Category
	}

	var wg sync.WaitGroup
	results := make(chan catResult, 8)

	categories := c.categoryFuncs()

	for _, cf := range categories {
		wg.Add(1)
		go func(idx int, fn func(string, *resolver.Resolver) Category) {
			defer wg.Done()
			cat := fn(domain, c.resolver)
			results <- catResult{index: idx, cat: cat}
		}(cf.index, cf.fn)
	}

	go func() {
		wg.Wait()
		close(results)
	}()

	ordered := make([]Category, len(categories))
	for cr := range results {
		ordered[cr.index] = cr.cat
	}

	var summary Summary
	for _, cat := range ordered {
		for _, check := range cat.Checks {
			switch check.Status {
			case StatusPass:
				summary.Pass++
			case StatusWarn:
				summary.Warn++
			case StatusFail:
				summary.Fail++
			case StatusInfo:
				summary.Info++
			}
		}
	}

	return &Report{
		Domain:     domain,
		Timestamp:  time.Now().UTC().Format(time.RFC3339),
		DurationMs: time.Since(start).Milliseconds(),
		Summary:    summary,
		Categories: ordered,
	}
}

// CheckStream runs all categories in parallel and sends each category as it completes.
func (c *Checker) CheckStream(domain string) <-chan StreamEvent {
	out := make(chan StreamEvent, 6)

	go func() {
		defer close(out)

		type catResult struct {
			index int
			cat   Category
		}

		var wg sync.WaitGroup
		results := make(chan catResult, 8)

		categories := c.categoryFuncs()

		for _, cf := range categories {
			wg.Add(1)
			go func(idx int, fn func(string, *resolver.Resolver) Category) {
				defer wg.Done()
				cat := fn(domain, c.resolver)
				results <- catResult{index: idx, cat: cat}
			}(cf.index, cf.fn)
		}

		go func() {
			wg.Wait()
			close(results)
		}()

		for cr := range results {
			out <- StreamEvent{
				Domain:   domain,
				Category: cr.cat,
			}
		}
	}()

	return out
}

type catFunc struct {
	index int
	fn    func(string, *resolver.Resolver) Category
}

func (c *Checker) categoryFuncs() []catFunc {
	return []catFunc{
		{0, checkOverview},
		{1, checkDomainWhois},
		{2, checkParent},
		{3, checkNS},
		{4, checkSOA},
		{5, checkMX},
		{6, checkMail},
		{7, checkWWW},
	}
}