// Package renderer provides Gantt chart rendering
package renderer

import (
	"fmt"
	"strings"

	"mermaid-go/pkg/ast"
)

// GanttRenderer implements Gantt chart rendering
type GanttRenderer struct{}

// NewGanttRenderer creates a new Gantt renderer
func NewGanttRenderer() *GanttRenderer {
	return &GanttRenderer{}
}

// Render renders a Gantt chart to mermaid syntax
func (r *GanttRenderer) Render(diagram *ast.GanttDiagram) (string, error) {
	var result strings.Builder

	// Start with gantt declaration
	result.WriteString("gantt\n")

	// Add title if present
	if diagram.Title != nil {
		result.WriteString(fmt.Sprintf("    title %s\n", *diagram.Title))
	}

	// Add date format if present
	if diagram.DateFormat != "" {
		result.WriteString(fmt.Sprintf("    dateFormat %s\n", diagram.DateFormat))
	}

	// Add axis format if not default
	if diagram.AxisFormat != "" && diagram.AxisFormat != "%Y-%m-%d" {
		result.WriteString(fmt.Sprintf("    axisFormat %s\n", diagram.AxisFormat))
	}

	// Render sections and tasks
	if len(diagram.Sections) > 0 {
		for _, section := range diagram.Sections {
			result.WriteString(fmt.Sprintf("    section %s\n", section.Name))
			for _, task := range section.Tasks {
				r.renderTask(&result, task)
			}
		}
	} else {
		// Render tasks without sections
		for _, task := range diagram.Tasks {
			r.renderTask(&result, task)
		}
	}

	return result.String(), nil
}

// renderTask renders a single task
func (r *GanttRenderer) renderTask(result *strings.Builder, task *ast.GanttTask) {
	result.WriteString(fmt.Sprintf("    %s : ", task.Name))

	// Add task data
	var taskData []string

	// Add dependencies first (task IDs)
	for _, dep := range task.Dependencies {
		taskData = append(taskData, dep)
	}

	// Add status if not default (only render explicit status)
	if task.Status != ast.GanttStatusActive {
		taskData = append(taskData, string(task.Status))
	}

	// Add start date
	if task.Start != nil {
		taskData = append(taskData, *task.Start)
	}

	// Add end date or duration
	if task.End != nil {
		taskData = append(taskData, *task.End)
	} else if task.Duration != nil {
		taskData = append(taskData, *task.Duration)
	}

	if len(taskData) > 0 {
		result.WriteString(strings.Join(taskData, " "))
	}

	result.WriteString("\n")
}