package cv

import (
	"fmt"
	"net/mail"
	"net/url"
	"strings"
)

// ValidationError represents a validation error with context
type ValidationError struct {
	Field   string
	Message string
}

func (e ValidationError) Error() string {
	return fmt.Sprintf("%s: %s", e.Field, e.Message)
}

// ValidationErrors is a collection of validation errors
type ValidationErrors []ValidationError

func (e ValidationErrors) Error() string {
	if len(e) == 0 {
		return ""
	}
	var sb strings.Builder
	sb.WriteString("validation failed:\n")
	for _, err := range e {
		sb.WriteString("  - ")
		sb.WriteString(err.Error())
		sb.WriteString("\n")
	}
	return sb.String()
}

// Validate performs comprehensive validation on the CV
func (cv *CV) Validate() error {
	var errors ValidationErrors

	// Validate Personal section
	if err := cv.Personal.Validate(); err != nil {
		if verrs, ok := err.(ValidationErrors); ok {
			errors = append(errors, verrs...)
		} else {
			errors = append(errors, ValidationError{Field: "personal", Message: err.Error()})
		}
	}

	// Validate Experience entries
	for i, exp := range cv.Experience {
		if err := exp.Validate(); err != nil {
			if verrs, ok := err.(ValidationErrors); ok {
				for _, verr := range verrs {
					errors = append(errors, ValidationError{
						Field:   fmt.Sprintf("experience[%d].%s", i, verr.Field),
						Message: verr.Message,
					})
				}
			} else {
				errors = append(errors, ValidationError{
					Field:   fmt.Sprintf("experience[%d]", i),
					Message: err.Error(),
				})
			}
		}
	}

	// Validate Education entries
	for i, edu := range cv.Education {
		if err := edu.Validate(); err != nil {
			if verrs, ok := err.(ValidationErrors); ok {
				for _, verr := range verrs {
					errors = append(errors, ValidationError{
						Field:   fmt.Sprintf("education[%d].%s", i, verr.Field),
						Message: verr.Message,
					})
				}
			} else {
				errors = append(errors, ValidationError{
					Field:   fmt.Sprintf("education[%d]", i),
					Message: err.Error(),
				})
			}
		}
	}

	// Validate Skills
	if err := cv.Skills.Validate(); err != nil {
		if verrs, ok := err.(ValidationErrors); ok {
			errors = append(errors, verrs...)
		} else {
			errors = append(errors, ValidationError{Field: "skills", Message: err.Error()})
		}
	}

	// Validate Languages
	for i, lang := range cv.Languages {
		if err := lang.Validate(); err != nil {
			if verrs, ok := err.(ValidationErrors); ok {
				for _, verr := range verrs {
					errors = append(errors, ValidationError{
						Field:   fmt.Sprintf("languages[%d].%s", i, verr.Field),
						Message: verr.Message,
					})
				}
			} else {
				errors = append(errors, ValidationError{
					Field:   fmt.Sprintf("languages[%d]", i),
					Message: err.Error(),
				})
			}
		}
	}

	// Validate Projects
	for i, proj := range cv.Projects {
		if err := proj.Validate(); err != nil {
			if verrs, ok := err.(ValidationErrors); ok {
				for _, verr := range verrs {
					errors = append(errors, ValidationError{
						Field:   fmt.Sprintf("projects[%d].%s", i, verr.Field),
						Message: verr.Message,
					})
				}
			} else {
				errors = append(errors, ValidationError{
					Field:   fmt.Sprintf("projects[%d]", i),
					Message: err.Error(),
				})
			}
		}
	}

	// Validate Meta (essential CV metadata)
	if err := cv.Meta.Validate(); err != nil {
		if verrs, ok := err.(ValidationErrors); ok {
			errors = append(errors, verrs...)
		} else {
			errors = append(errors, ValidationError{Field: "meta", Message: err.Error()})
		}
	}

	if len(errors) > 0 {
		return errors
	}
	return nil
}

// Validate checks Personal information
func (p *Personal) Validate() error {
	var errors ValidationErrors

	if strings.TrimSpace(p.Name) == "" {
		errors = append(errors, ValidationError{Field: "name", Message: "name is required"})
	}

	if strings.TrimSpace(p.Email) == "" {
		errors = append(errors, ValidationError{Field: "email", Message: "email is required"})
	} else if !isValidEmail(p.Email) {
		errors = append(errors, ValidationError{Field: "email", Message: "invalid email format"})
	}

	// Validate URLs if present
	if p.LinkedIn != "" && !isValidURL(p.LinkedIn) {
		errors = append(errors, ValidationError{Field: "linkedin", Message: "invalid URL format"})
	}
	if p.GitHub != "" && !isValidURL(p.GitHub) {
		errors = append(errors, ValidationError{Field: "github", Message: "invalid URL format"})
	}
	if p.Website != "" && !isValidURL(p.Website) {
		errors = append(errors, ValidationError{Field: "website", Message: "invalid URL format"})
	}
	if p.Domestika != "" && !isValidURL(p.Domestika) {
		errors = append(errors, ValidationError{Field: "domestika", Message: "invalid URL format"})
	}

	if len(errors) > 0 {
		return errors
	}
	return nil
}

// Validate checks Experience entry
func (e *Experience) Validate() error {
	var errors ValidationErrors

	if strings.TrimSpace(e.Position) == "" {
		errors = append(errors, ValidationError{Field: "position", Message: "position is required"})
	}
	if strings.TrimSpace(e.Company) == "" {
		errors = append(errors, ValidationError{Field: "company", Message: "company is required"})
	}
	if strings.TrimSpace(e.StartDate) == "" {
		errors = append(errors, ValidationError{Field: "startDate", Message: "start date is required"})
	}

	// EndDate is only required if not current
	if !e.Current && strings.TrimSpace(e.EndDate) == "" {
		errors = append(errors, ValidationError{Field: "endDate", Message: "end date is required when current is false"})
	}

	// Validate company URL if present
	if e.CompanyURL != "" && !isValidURL(e.CompanyURL) {
		errors = append(errors, ValidationError{Field: "companyURL", Message: "invalid URL format"})
	}

	if len(errors) > 0 {
		return errors
	}
	return nil
}

// Validate checks Education entry
func (e *Education) Validate() error {
	var errors ValidationErrors

	if strings.TrimSpace(e.Degree) == "" {
		errors = append(errors, ValidationError{Field: "degree", Message: "degree is required"})
	}
	if strings.TrimSpace(e.Institution) == "" {
		errors = append(errors, ValidationError{Field: "institution", Message: "institution is required"})
	}
	if strings.TrimSpace(e.StartDate) == "" {
		errors = append(errors, ValidationError{Field: "startDate", Message: "start date is required"})
	}
	if strings.TrimSpace(e.EndDate) == "" {
		errors = append(errors, ValidationError{Field: "endDate", Message: "end date is required"})
	}

	if len(errors) > 0 {
		return errors
	}
	return nil
}

// Validate checks Skills section
func (s *Skills) Validate() error {
	var errors ValidationErrors

	for i, cat := range s.Technical {
		if strings.TrimSpace(cat.Category) == "" {
			errors = append(errors, ValidationError{
				Field:   fmt.Sprintf("technical[%d].category", i),
				Message: "category name is required",
			})
		}

		// Proficiency should be between 1-10 (half-star increments over 5 stars)
		if cat.Proficiency < 1 || cat.Proficiency > 10 {
			errors = append(errors, ValidationError{
				Field:   fmt.Sprintf("technical[%d].proficiency", i),
				Message: "proficiency must be between 1 and 10",
			})
		}

		if len(cat.Items) == 0 {
			errors = append(errors, ValidationError{
				Field:   fmt.Sprintf("technical[%d].items", i),
				Message: "at least one skill item is required",
			})
		}

		// Validate sidebar value
		if cat.Sidebar != "" && cat.Sidebar != "left" && cat.Sidebar != "right" {
			errors = append(errors, ValidationError{
				Field:   fmt.Sprintf("technical[%d].sidebar", i),
				Message: "sidebar must be 'left', 'right', or empty",
			})
		}
	}

	if len(errors) > 0 {
		return errors
	}
	return nil
}

// Validate checks Language entry
func (l *Language) Validate() error {
	var errors ValidationErrors

	if strings.TrimSpace(l.Language) == "" {
		errors = append(errors, ValidationError{Field: "language", Message: "language name is required"})
	}

	if strings.TrimSpace(l.Proficiency) == "" {
		errors = append(errors, ValidationError{Field: "proficiency", Message: "proficiency is required"})
	}

	// Level should be between 1-5 (typical language proficiency scale)
	if l.Level < 1 || l.Level > 5 {
		errors = append(errors, ValidationError{Field: "level", Message: "level must be between 1 and 5"})
	}

	if len(errors) > 0 {
		return errors
	}
	return nil
}

// Validate checks Project entry
func (p *Project) Validate() error {
	var errors ValidationErrors

	if strings.TrimSpace(p.Title) == "" {
		errors = append(errors, ValidationError{Field: "title", Message: "title is required"})
	}

	// Validate URL if present
	if p.URL != "" && !isValidURL(p.URL) {
		errors = append(errors, ValidationError{Field: "url", Message: "invalid URL format"})
	}

	// GitRepoUrl can be either a URL or a local filesystem path
	// We don't validate it strictly since it supports both formats

	if len(errors) > 0 {
		return errors
	}
	return nil
}

// Validate checks Meta information
func (m *Meta) Validate() error {
	var errors ValidationErrors

	if strings.TrimSpace(m.Version) == "" {
		errors = append(errors, ValidationError{Field: "version", Message: "version is required"})
	}

	if strings.TrimSpace(m.Language) == "" {
		errors = append(errors, ValidationError{Field: "language", Message: "language is required"})
	}

	if len(errors) > 0 {
		return errors
	}
	return nil
}

// Helper functions

// isValidEmail checks if an email address is valid
func isValidEmail(email string) bool {
	email = strings.TrimSpace(email)
	if email == "" {
		return false
	}
	_, err := mail.ParseAddress(email)
	return err == nil
}

// isValidURL checks if a URL is valid
func isValidURL(urlStr string) bool {
	urlStr = strings.TrimSpace(urlStr)
	if urlStr == "" {
		return false
	}

	// Parse the URL
	u, err := url.Parse(urlStr)
	if err != nil {
		return false
	}

	// Check that it has a scheme (http, https, etc.)
	if u.Scheme == "" {
		return false
	}

	// Check that it has a host
	if u.Host == "" {
		return false
	}

	return true
}