package publications

import (
	"context"
	"fmt"
	"log"
	"sync"
	"time"

	"github.com/breakpilot/edu-search-service/internal/database"
	"github.com/google/uuid"
)

// PublicationCrawler crawls publications for university staff
type PublicationCrawler struct {
	repo           *database.Repository
	crossref       *CrossRefClient
	rateLimit      time.Duration
	mu             sync.Mutex
	lastRequest    time.Time
}

// CrawlResult contains the result of a publication crawl
type CrawlResult struct {
	StaffID       uuid.UUID
	PubsFound     int
	PubsNew       int
	PubsUpdated   int
	Errors        []string
	Duration      time.Duration
}

// NewPublicationCrawler creates a new publication crawler
func NewPublicationCrawler(repo *database.Repository, email string) *PublicationCrawler {
	return &PublicationCrawler{
		repo:      repo,
		crossref:  NewCrossRefClient(email),
		rateLimit: time.Second, // CrossRef polite pool: 50 req/sec max
	}
}

// CrawlForStaff crawls publications for a single staff member
func (c *PublicationCrawler) CrawlForStaff(ctx context.Context, staff *database.UniversityStaff) (*CrawlResult, error) {
	start := time.Now()
	result := &CrawlResult{
		StaffID: staff.ID,
	}

	log.Printf("Starting publication crawl for %s", *staff.FullName)

	var pubs []*database.Publication

	// Strategy 1: Search by ORCID (most reliable)
	if staff.ORCID != nil && *staff.ORCID != "" {
		c.waitForRateLimit()
		orcidPubs, err := c.crossref.SearchByORCID(ctx, *staff.ORCID, 100)
		if err != nil {
			result.Errors = append(result.Errors, fmt.Sprintf("ORCID search error: %v", err))
		} else {
			pubs = append(pubs, orcidPubs...)
			log.Printf("Found %d publications via ORCID for %s", len(orcidPubs), *staff.FullName)
		}
	}

	// Strategy 2: Search by author name
	if staff.FullName != nil && *staff.FullName != "" {
		c.waitForRateLimit()
		namePubs, err := c.crossref.SearchByAuthor(ctx, *staff.FullName, 50)
		if err != nil {
			result.Errors = append(result.Errors, fmt.Sprintf("Name search error: %v", err))
		} else {
			// Deduplicate
			for _, pub := range namePubs {
				if !containsPub(pubs, pub) {
					pubs = append(pubs, pub)
				}
			}
			log.Printf("Found %d additional publications via name search for %s", len(namePubs), *staff.FullName)
		}
	}

	// Save publications and create links
	for _, pub := range pubs {
		// Save publication
		err := c.repo.CreatePublication(ctx, pub)
		if err != nil {
			result.Errors = append(result.Errors, fmt.Sprintf("Save error for %s: %v", pub.Title, err))
			continue
		}

		result.PubsFound++

		// Link to staff
		link := &database.StaffPublication{
			StaffID:       staff.ID,
			PublicationID: pub.ID,
		}

		// Determine author position
		pos := findAuthorPosition(pub, staff)
		if pos > 0 {
			link.AuthorPosition = &pos
		}

		if err := c.repo.LinkStaffPublication(ctx, link); err != nil {
			result.Errors = append(result.Errors, fmt.Sprintf("Link error: %v", err))
		}
	}

	result.Duration = time.Since(start)

	log.Printf("Completed publication crawl for %s: found=%d, duration=%v",
		*staff.FullName, result.PubsFound, result.Duration)

	return result, nil
}

// CrawlForUniversity crawls publications for all staff at a university
func (c *PublicationCrawler) CrawlForUniversity(ctx context.Context, uniID uuid.UUID, limit int) (*database.UniversityCrawlStatus, error) {
	log.Printf("Starting publication crawl for university %s", uniID)

	// Get staff with ORCID first (more reliable)
	params := database.StaffSearchParams{
		UniversityID: &uniID,
		Limit:        limit,
	}

	result, err := c.repo.SearchStaff(ctx, params)
	if err != nil {
		return nil, err
	}

	status := &database.UniversityCrawlStatus{
		UniversityID:     uniID,
		PubCrawlStatus:   "running",
	}

	var totalPubs int
	var errors []string

	for _, staff := range result.Staff {
		select {
		case <-ctx.Done():
			status.PubCrawlStatus = "cancelled"
			status.PubErrors = append(errors, "Crawl cancelled")
			return status, ctx.Err()
		default:
		}

		crawlResult, err := c.CrawlForStaff(ctx, &staff)
		if err != nil {
			errors = append(errors, fmt.Sprintf("%s: %v", staff.LastName, err))
			continue
		}

		totalPubs += crawlResult.PubsFound
		errors = append(errors, crawlResult.Errors...)
	}

	now := time.Now()
	status.LastPubCrawl = &now
	status.PubCrawlStatus = "completed"
	status.PubCount = totalPubs
	status.PubErrors = errors

	// Update status in database
	if err := c.repo.UpdateCrawlStatus(ctx, status); err != nil {
		log.Printf("Warning: Failed to update crawl status: %v", err)
	}

	log.Printf("Completed publication crawl for university %s: %d publications found", uniID, totalPubs)

	return status, nil
}

// ResolveDOI resolves a DOI and saves the publication
func (c *PublicationCrawler) ResolveDOI(ctx context.Context, doi string) (*database.Publication, error) {
	c.waitForRateLimit()

	pub, err := c.crossref.GetWorkByDOI(ctx, doi)
	if err != nil {
		return nil, err
	}

	if err := c.repo.CreatePublication(ctx, pub); err != nil {
		return nil, err
	}

	return pub, nil
}

// waitForRateLimit enforces rate limiting
func (c *PublicationCrawler) waitForRateLimit() {
	c.mu.Lock()
	defer c.mu.Unlock()

	elapsed := time.Since(c.lastRequest)
	if elapsed < c.rateLimit {
		time.Sleep(c.rateLimit - elapsed)
	}

	c.lastRequest = time.Now()
}

// containsPub checks if a publication is already in the list (by DOI or title)
func containsPub(pubs []*database.Publication, pub *database.Publication) bool {
	for _, existing := range pubs {
		// Check DOI
		if pub.DOI != nil && existing.DOI != nil && *pub.DOI == *existing.DOI {
			return true
		}
		// Check title (rough match)
		if pub.Title == existing.Title {
			return true
		}
	}
	return false
}

// findAuthorPosition finds the position of a staff member in the author list
func findAuthorPosition(pub *database.Publication, staff *database.UniversityStaff) int {
	for i, author := range pub.Authors {
		// Check if author name matches staff
		if staff.LastName != "" && containsIgnoreCase(author, staff.LastName) {
			return i + 1
		}
	}
	return 0
}

// containsIgnoreCase checks if s contains substr (case insensitive)
func containsIgnoreCase(s, substr string) bool {
	return len(s) >= len(substr) &&
		(s == substr ||
			len(substr) == 0 ||
			(len(s) > 0 && containsIgnoreCaseHelper(s, substr)))
}

func containsIgnoreCaseHelper(s, substr string) bool {
	for i := 0; i <= len(s)-len(substr); i++ {
		if equalFold(s[i:i+len(substr)], substr) {
			return true
		}
	}
	return false
}

func equalFold(s1, s2 string) bool {
	if len(s1) != len(s2) {
		return false
	}
	for i := 0; i < len(s1); i++ {
		c1, c2 := s1[i], s2[i]
		if c1 != c2 {
			// Simple ASCII case folding
			if c1 >= 'A' && c1 <= 'Z' {
				c1 += 'a' - 'A'
			}
			if c2 >= 'A' && c2 <= 'Z' {
				c2 += 'a' - 'A'
			}
			if c1 != c2 {
				return false
			}
		}
	}
	return true
}