package delta

import (
	"net/http"
	"os"
	"path/filepath"

	"github.com/gin-gonic/gin"
)

// Handler provides delta patch generation for JAR artefacts.
type Handler struct {
	artefactDir string
}

func NewHandler(artefactDir string) *Handler {
	return &Handler{artefactDir: artefactDir}
}

// GenerateDelta creates a delta patch between two artefact versions.
// POST /api/v1/delta/generate
// Form fields: oldVersion, newVersion
func (h *Handler) GenerateDelta(c *gin.Context) {
	oldVersion := c.PostForm("oldVersion")
	newVersion := c.PostForm("newVersion")
	if oldVersion == "" || newVersion == "" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "oldVersion and newVersion are required"})
		return
	}

	oldDir := filepath.Join(h.artefactDir, oldVersion)
	newDir := filepath.Join(h.artefactDir, newVersion)

	if _, err := os.Stat(oldDir); os.IsNotExist(err) {
		c.JSON(http.StatusNotFound, gin.H{"error": "Old version not found: " + oldVersion})
		return
	}
	if _, err := os.Stat(newDir); os.IsNotExist(err) {
		c.JSON(http.StatusNotFound, gin.H{"error": "New version not found: " + newVersion})
		return
	}

	// Find JAR files in each version directory
	oldJar, err := findJarInDir(oldDir)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "No JAR found in old version: " + err.Error()})
		return
	}
	newJar, err := findJarInDir(newDir)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "No JAR found in new version: " + err.Error()})
		return
	}

	patchPath := filepath.Join(h.artefactDir, "patches", oldVersion+"-to-"+newVersion+".patch")
	if err := os.MkdirAll(filepath.Dir(patchPath), 0755); err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to create patch directory"})
		return
	}

	if err := GenerateJarDelta(oldJar, newJar, patchPath); err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Delta generation failed: " + err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"status":     "generated",
		"patchPath":  patchPath,
		"oldVersion": oldVersion,
		"newVersion": newVersion,
	})
}

func findJarInDir(dir string) (string, error) {
	entries, err := os.ReadDir(dir)
	if err != nil {
		return "", err
	}
	for _, e := range entries {
		if !e.IsDir() && filepath.Ext(e.Name()) == ".jar" {
			return filepath.Join(dir, e.Name()), nil
		}
	}
	return "", os.ErrNotExist
}