package gallery

import (
	"crypto/sha256"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"

	"github.com/rs/zerolog/log"
	"gopkg.in/yaml.v2"
)

/*

description: |
    foo
license: ""

urls:
-
-

name: "bar"

config_file: |
    # Note, name will be injected. or generated by the alias wanted by the user
    threads: 14

files:
    - filename: ""
      sha: ""
      uri: ""

prompt_templates:
    - name: ""
      content: ""

*/

type Config struct {
	Description     string           `yaml:"description"`
	License         string           `yaml:"license"`
	URLs            []string         `yaml:"urls"`
	Name            string           `yaml:"name"`
	ConfigFile      string           `yaml:"config_file"`
	Files           []File           `yaml:"files"`
	PromptTemplates []PromptTemplate `yaml:"prompt_templates"`
}

type File struct {
	Filename string `yaml:"filename" json:"filename"`
	SHA256   string `yaml:"sha256" json:"sha256"`
	URI      string `yaml:"uri" json:"uri"`
}

type PromptTemplate struct {
	Name    string `yaml:"name"`
	Content string `yaml:"content"`
}

func ReadConfigFile(filePath string) (*Config, error) {
	// Read the YAML file
	yamlFile, err := os.ReadFile(filePath)
	if err != nil {
		return nil, fmt.Errorf("failed to read YAML file: %v", err)
	}

	// Unmarshal YAML data into a Config struct
	var config Config
	err = yaml.Unmarshal(yamlFile, &config)
	if err != nil {
		return nil, fmt.Errorf("failed to unmarshal YAML: %v", err)
	}

	return &config, nil
}

func inTrustedRoot(path string, trustedRoot string) error {
	for path != "/" {
		path = filepath.Dir(path)
		if path == trustedRoot {
			return nil
		}
	}
	return fmt.Errorf("path is outside of trusted root")
}

func verifyPath(path, basePath string) error {
	c := filepath.Clean(filepath.Join(basePath, path))
	return inTrustedRoot(c, basePath)
}

func Apply(basePath, nameOverride string, config *Config) error {
	// Create base path if it doesn't exist
	err := os.MkdirAll(basePath, 0755)
	if err != nil {
		return fmt.Errorf("failed to create base path: %v", err)
	}

	// Download files and verify their SHA
	for _, file := range config.Files {
		log.Debug().Msgf("Checking %q exists and matches SHA", file.Filename)

		if err := verifyPath(file.Filename, basePath); err != nil {
			return err
		}
		// Create file path
		filePath := filepath.Join(basePath, file.Filename)

		// Check if the file already exists
		_, err := os.Stat(filePath)
		if err == nil {
			// File exists, check SHA
			if file.SHA256 != "" {
				// Verify SHA
				calculatedSHA, err := calculateSHA(filePath)
				if err != nil {
					return fmt.Errorf("failed to calculate SHA for file %q: %v", file.Filename, err)
				}
				if calculatedSHA == file.SHA256 {
					// SHA matches, skip downloading
					log.Debug().Msgf("File %q already exists and matches the SHA. Skipping download", file.Filename)
					continue
				}
				// SHA doesn't match, delete the file and download again
				err = os.Remove(filePath)
				if err != nil {
					return fmt.Errorf("failed to remove existing file %q: %v", file.Filename, err)
				}
				log.Debug().Msgf("Removed %q (SHA doesn't match)", filePath)

			} else {
				// SHA is missing, skip downloading
				log.Debug().Msgf("File %q already exists. Skipping download", file.Filename)
				continue
			}
		} else if !os.IsNotExist(err) {
			// Error occurred while checking file existence
			return fmt.Errorf("failed to check file %q existence: %v", file.Filename, err)
		}

		log.Debug().Msgf("Downloading %q", file.URI)

		// Download file
		resp, err := http.Get(file.URI)
		if err != nil {
			return fmt.Errorf("failed to download file %q: %v", file.Filename, err)
		}
		defer resp.Body.Close()

		// Create parent directory
		err = os.MkdirAll(filepath.Dir(filePath), 0755)
		if err != nil {
			return fmt.Errorf("failed to create parent directory for file %q: %v", file.Filename, err)
		}

		// Create and write file content
		outFile, err := os.Create(filePath)
		if err != nil {
			return fmt.Errorf("failed to create file %q: %v", file.Filename, err)
		}
		defer outFile.Close()

		if file.SHA256 != "" {
			log.Debug().Msgf("Download and verifying %q", file.Filename)

			// Write file content and calculate SHA
			hash := sha256.New()
			_, err = io.Copy(io.MultiWriter(outFile, hash), resp.Body)
			if err != nil {
				return fmt.Errorf("failed to write file %q: %v", file.Filename, err)
			}

			// Verify SHA
			calculatedSHA := fmt.Sprintf("%x", hash.Sum(nil))
			if calculatedSHA != file.SHA256 {
				return fmt.Errorf("SHA mismatch for file %q ( calculated: %s != metadata: %s )", file.Filename, calculatedSHA, file.SHA256)
			}
		} else {
			log.Debug().Msgf("SHA missing for %q. Skipping validation", file.Filename)
			_, err = io.Copy(outFile, resp.Body)
			if err != nil {
				return fmt.Errorf("failed to write file %q: %v", file.Filename, err)
			}
		}

		log.Debug().Msgf("File %q downloaded and verified", file.Filename)
	}

	// Write prompt template contents to separate files
	for _, template := range config.PromptTemplates {
		if err := verifyPath(template.Name+".tmpl", basePath); err != nil {
			return err
		}
		// Create file path
		filePath := filepath.Join(basePath, template.Name+".tmpl")

		// Create parent directory
		err := os.MkdirAll(filepath.Dir(filePath), 0755)
		if err != nil {
			return fmt.Errorf("failed to create parent directory for prompt template %q: %v", template.Name, err)
		}
		// Create and write file content
		err = os.WriteFile(filePath, []byte(template.Content), 0644)
		if err != nil {
			return fmt.Errorf("failed to write prompt template %q: %v", template.Name, err)
		}

		log.Debug().Msgf("Prompt template %q written", template.Name)
	}

	name := config.Name
	if nameOverride != "" {
		name = nameOverride
	}

	if err := verifyPath(name+".yaml", basePath); err != nil {
		return err
	}

	configFilePath := filepath.Join(basePath, name+".yaml")

	// Read and update config file as map[string]interface{}
	configMap := make(map[string]interface{})
	err = yaml.Unmarshal([]byte(config.ConfigFile), &configMap)
	if err != nil {
		return fmt.Errorf("failed to unmarshal config YAML: %v", err)
	}

	configMap["name"] = name

	// Write updated config file
	updatedConfigYAML, err := yaml.Marshal(configMap)
	if err != nil {
		return fmt.Errorf("failed to marshal updated config YAML: %v", err)
	}

	err = os.WriteFile(configFilePath, updatedConfigYAML, 0644)
	if err != nil {
		return fmt.Errorf("failed to write updated config file: %v", err)
	}

	log.Debug().Msgf("Written config file %s", configFilePath)
	return nil
}

func calculateSHA(filePath string) (string, error) {
	file, err := os.Open(filePath)
	if err != nil {
		return "", err
	}
	defer file.Close()

	hash := sha256.New()
	if _, err := io.Copy(hash, file); err != nil {
		return "", err
	}

	return fmt.Sprintf("%x", hash.Sum(nil)), nil
}