package handlers

import (
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing/object"

	c "github.com/juanatsap/cv-site/internal/constants"
	cvmodel "github.com/juanatsap/cv-site/internal/models/cv"
)

// ==============================================================================
// SKILLS HELPERS
// ==============================================================================

// splitSkills splits skill categories between left (page 1) and right (page 2) sidebars
// Each category explicitly specifies which sidebar it belongs to via the "sidebar" field
func splitSkills(skills []cvmodel.SkillCategory) (left, right []cvmodel.SkillCategory) {
	if len(skills) == 0 {
		return nil, nil
	}

	// Filter by sidebar field
	for _, skill := range skills {
		if skill.Sidebar == "right" {
			right = append(right, skill)
		} else {
			// Default to left if not specified or if set to "left"
			left = append(left, skill)
		}
	}

	return left, right
}

// ==============================================================================
// DATE/DURATION HELPERS
// ==============================================================================

// calculateYearsOfExperience calculates years of experience since April 1, 2005
// This matches the original React implementation that calculated from 01/04/2005
func calculateYearsOfExperience() int {
	// First day at work: April 1, 2005
	firstDay := time.Date(2005, time.April, 1, 9, 0, 0, 0, time.UTC)

	// Current date
	now := time.Now()

	// Calculate the difference in years
	years := now.Year() - firstDay.Year()

	// Adjust if we haven't reached the anniversary this year yet
	if now.Month() < firstDay.Month() ||
		(now.Month() == firstDay.Month() && now.Day() < firstDay.Day()) {
		years--
	}

	return years
}

// calculateDuration calculates the duration between two dates in years and months
// Date format expected: "YYYY-MM" (e.g., "2021-01")
// Returns a formatted string like "3 years 6 months" or "6 months"
func calculateDuration(startDate, endDate string, current bool, lang string) string {
	// Parse start date
	start, err := time.Parse("2006-01", startDate)
	if err != nil {
		return ""
	}

	// Determine end date
	var end time.Time
	if current {
		end = time.Now()
	} else {
		end, err = time.Parse("2006-01", endDate)
		if err != nil {
			return ""
		}
	}

	// Calculate total months
	totalMonths := (end.Year()-start.Year())*12 + int(end.Month()-start.Month())

	// If end date is before start date, return empty
	if totalMonths < 0 {
		return ""
	}

	years := totalMonths / 12
	months := totalMonths % 12

	// Format the duration string based on language
	var result string
	if lang == "es" {
		if years > 0 && months > 0 {
			yearStr := "años"
			if years == 1 {
				yearStr = "año"
			}
			monthStr := "meses"
			if months == 1 {
				monthStr = "mes"
			}
			result = fmt.Sprintf("(%d %s %d %s)", years, yearStr, months, monthStr)
		} else if years > 0 {
			yearStr := "años"
			if years == 1 {
				yearStr = "año"
			}
			result = fmt.Sprintf("(%d %s)", years, yearStr)
		} else {
			monthStr := "meses"
			if months == 1 {
				monthStr = "mes"
			}
			result = fmt.Sprintf("(%d %s)", months, monthStr)
		}
	} else {
		if years > 0 && months > 0 {
			yearStr := "years"
			if years == 1 {
				yearStr = "year"
			}
			monthStr := "months"
			if months == 1 {
				monthStr = "month"
			}
			result = fmt.Sprintf("(%d %s %d %s)", years, yearStr, months, monthStr)
		} else if years > 0 {
			yearStr := "years"
			if years == 1 {
				yearStr = "year"
			}
			result = fmt.Sprintf("(%d %s)", years, yearStr)
		} else {
			monthStr := "months"
			if months == 1 {
				monthStr = "month"
			}
			result = fmt.Sprintf("(%d %s)", months, monthStr)
		}
	}

	return result
}

// processProjectDates calculates dynamic dates for projects
// If a project has a gitRepoUrl, it fetches the first commit date using go-git
// For current projects, it sets the current system date
func processProjectDates(project *cvmodel.Project, lang string) {
	now := time.Now()

	// Set dynamic current date for ongoing projects
	if project.Current {
		if lang == "es" {
			project.DynamicDate = "Presente"
		} else {
			project.DynamicDate = "Present"
		}
	}

	// If project has a git repository path, fetch the first commit date
	if project.GitRepoUrl != "" {
		commitDate := getGitRepoFirstCommitDate(project.GitRepoUrl)
		if commitDate != "" {
			project.ComputedStartDate = commitDate
		}
	}

	// If no computed date and no static date, use current date for current projects
	if project.ComputedStartDate == "" && project.StartDate == "" && project.Current {
		project.ComputedStartDate = now.Format("2006-01")
	}

	// If we have a computed date but no static date, use the computed one
	if project.ComputedStartDate != "" && project.StartDate == "" {
		project.StartDate = project.ComputedStartDate
	}
}

// ==============================================================================
// GIT HELPERS (using go-git - pure Go implementation, no shell commands)
// ==============================================================================

// findProjectRoot finds the project root directory by looking for .git directory
func findProjectRoot() (string, error) {
	cwd, err := os.Getwd()
	if err != nil {
		return "", err
	}

	dir := cwd
	for {
		gitPath := filepath.Join(dir, ".git")
		if info, err := os.Stat(gitPath); err == nil && info.IsDir() {
			return dir, nil
		}

		parent := filepath.Dir(dir)
		if parent == dir {
			return cwd, nil
		}
		dir = parent
	}
}

// validateRepoPath validates that a repository path is safe to use
// Security: Prevents path traversal attacks by ensuring path is within project directory
func validateRepoPath(path string) error {
	absPath, err := filepath.Abs(path)
	if err != nil {
		return fmt.Errorf("invalid path: %w", err)
	}

	projectRoot, err := findProjectRoot()
	if err != nil {
		return fmt.Errorf("cannot determine project root: %w", err)
	}

	// Security: Only allow paths within project directory
	if !strings.HasPrefix(absPath, projectRoot) {
		return fmt.Errorf("repository path outside project directory: %s", path)
	}

	info, err := os.Stat(absPath)
	if err != nil {
		return fmt.Errorf("path does not exist: %w", err)
	}
	if !info.IsDir() {
		return fmt.Errorf("path is not a directory: %s", path)
	}

	return nil
}

// getGitRepoFirstCommitDate fetches the first commit date from a git repository
// Uses go-git (pure Go) - no shell command execution, eliminating injection risks
func getGitRepoFirstCommitDate(repoPath string) string {
	// Security: Validate repository path
	if err := validateRepoPath(repoPath); err != nil {
		log.Printf("Security: Rejected git operation for invalid path %s: %v", repoPath, err)
		return ""
	}

	// Open the repository using go-git
	repo, err := git.PlainOpen(repoPath)
	if err != nil {
		log.Printf("Failed to open git repository at %s: %v", repoPath, err)
		return ""
	}

	// Get the commit history
	commitIter, err := repo.Log(&git.LogOptions{
		Order: git.LogOrderCommitterTime,
	})
	if err != nil {
		log.Printf("Failed to get commit log for %s: %v", repoPath, err)
		return ""
	}
	defer commitIter.Close()

	// Find the oldest commit by iterating through all commits
	var oldestCommit *object.Commit
	err = commitIter.ForEach(func(c *object.Commit) error {
		if oldestCommit == nil || c.Committer.When.Before(oldestCommit.Committer.When) {
			oldestCommit = c
		}
		return nil
	})
	if err != nil {
		log.Printf("Error iterating commits for %s: %v", repoPath, err)
		return ""
	}

	if oldestCommit == nil {
		log.Printf("No commits found in repository %s", repoPath)
		return ""
	}

	// Return date in YYYY-MM format
	return oldestCommit.Committer.When.Format("2006-01")
}

// ==============================================================================
// TEMPLATE DATA PREPARATION
// ==============================================================================

// prepareTemplateData prepares common template data used across handlers
func (h *CVHandler) prepareTemplateData(lang string) (map[string]interface{}, error) {
	// Get CV data from cache
	cachedCV := h.dataCache.GetCV(lang)
	if cachedCV == nil {
		return nil, fmt.Errorf("CV data not found for language: %s", lang)
	}

	// Get UI translations from cache
	ui := h.dataCache.GetUI(lang)
	if ui == nil {
		return nil, fmt.Errorf("UI data not found for language: %s", lang)
	}

	// Create a working copy of CV to avoid mutating cached data
	cv := *cachedCV

	// Deep copy Experience slice (we modify Duration field)
	cv.Experience = make([]cvmodel.Experience, len(cachedCV.Experience))
	copy(cv.Experience, cachedCV.Experience)

	// Deep copy Projects slice (we modify computed fields)
	cv.Projects = make([]cvmodel.Project, len(cachedCV.Projects))
	copy(cv.Projects, cachedCV.Projects)

	// Calculate duration for each experience
	for i := range cv.Experience {
		cv.Experience[i].Duration = calculateDuration(
			cv.Experience[i].StartDate,
			cv.Experience[i].EndDate,
			cv.Experience[i].Current,
			lang,
		)
	}

	// Process projects for dynamic dates
	for i := range cv.Projects {
		processProjectDates(&cv.Projects[i], lang)
	}

	// Split skills between left and right sidebars
	skillsLeft, skillsRight := splitSkills(cachedCV.Skills.Technical)

	// Calculate years of experience
	yearsOfExperience := calculateYearsOfExperience()

	// Get current year
	currentYear := time.Now().Year()

	// Check if production mode AND CSS bundle exists
	// This ensures graceful fallback to modular CSS if bundle not built
	isProduction := os.Getenv(c.EnvVarGOEnv) == c.EnvProduction
	if isProduction {
		bundlePath := filepath.Join(c.DirStatic, "dist", "bundle.min.css")
		if _, err := os.Stat(bundlePath); os.IsNotExist(err) {
			// Bundle doesn't exist, fall back to modular CSS
			isProduction = false
		}
	}

	// Prepare template data
	data := map[string]interface{}{
		"CV":                &cv,
		"UI":                ui,
		"Lang":              lang,
		"SkillsLeft":        skillsLeft,
		"SkillsRight":       skillsRight,
		"YearsOfExperience": yearsOfExperience,
		"CurrentYear":       currentYear,
		"IsProduction":      isProduction,
		"CanonicalURL":      fmt.Sprintf("https://juan.andres.morenorub.io/?lang=%s", lang),
		"AlternateEN":       "https://juan.andres.morenorub.io/?lang=en",
		"AlternateES":       "https://juan.andres.morenorub.io/?lang=es",
		"ChatEnabled":       h.chatEnabled,
	}

	return data, nil
}

// ==============================================================================
// COOKIE HELPERS
// ==============================================================================
// Note: Cookie preference management is now handled client-side via JavaScript
// and localStorage. Server-side cookie helpers have been removed as unused.