package bundle

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"time"
)

type rawManifest struct {
	SchemaVersion *int              `json:"schema_version"`
	ID            *string           `json:"id"`
	Digest        *string           `json:"digest"`
	Created       *string           `json:"created"`
	Files         []rawManifestFile `json:"files"`
}

type rawManifestFile struct {
	Path   *string `json:"path"`
	SHA256 *string `json:"sha256"`
	Size   *int64  `json:"size"`
}

func ParseManifest(data []byte) (Manifest, error) {
	decoder := json.NewDecoder(bytes.NewReader(data))
	var raw rawManifest
	if err := decoder.Decode(&raw); err != nil {
		return Manifest{}, fmt.Errorf("parse manifest: %w", err)
	}
	var extra any
	if err := decoder.Decode(&extra); err != io.EOF {
		return Manifest{}, fmt.Errorf("parse manifest: trailing data")
	}

	var manifest Manifest
	if raw.SchemaVersion == nil {
		return Manifest{}, fmt.Errorf("manifest schema_version is required")
	}
	manifest.SchemaVersion = *raw.SchemaVersion
	if raw.ID == nil || *raw.ID == "" {
		return Manifest{}, fmt.Errorf("manifest id is required")
	}
	manifest.ID = *raw.ID
	if raw.Digest == nil || *raw.Digest == "" {
		return Manifest{}, fmt.Errorf("manifest digest is required")
	}
	manifest.Digest = *raw.Digest
	if raw.Created == nil || *raw.Created == "" {
		return Manifest{}, fmt.Errorf("manifest created is required")
	}
	created, err := time.Parse(time.RFC3339, *raw.Created)
	if err != nil {
		return Manifest{}, fmt.Errorf("manifest created must be RFC3339: %w", err)
	}
	manifest.Created = created
	if len(raw.Files) == 0 {
		return Manifest{}, fmt.Errorf("manifest files is required")
	}

	for index, rawFile := range raw.Files {
		file, err := parseManifestFile(index, rawFile)
		if err != nil {
			return Manifest{}, err
		}
		manifest.Files = append(manifest.Files, file)
	}
	if err := ValidateManifest(manifest); err != nil {
		return Manifest{}, fmt.Errorf("manifest %w", err)
	}
	return manifest, nil
}

func parseManifestFile(index int, raw rawManifestFile) (ManifestFile, error) {
	if raw.Path == nil || *raw.Path == "" {
		return ManifestFile{}, fmt.Errorf("manifest files[%d].path is required", index)
	}
	if raw.SHA256 == nil || *raw.SHA256 == "" {
		return ManifestFile{}, fmt.Errorf("manifest files[%d].sha256 is required", index)
	}
	if raw.Size == nil {
		return ManifestFile{}, fmt.Errorf("manifest files[%d].size is required", index)
	}
	return ManifestFile{
		Path:   *raw.Path,
		SHA256: *raw.SHA256,
		Size:   *raw.Size,
	}, nil
}

func MarshalManifest(manifest Manifest) ([]byte, error) {
	if err := ValidateManifest(manifest); err != nil {
		return nil, err
	}
	data, err := json.MarshalIndent(manifest, "", "  ")
	if err != nil {
		return nil, err
	}
	return append(data, '\n'), nil
}

func LoadManifest(root string) (Manifest, error) {
	data, err := os.ReadFile(filepath.Join(root, ManifestName))
	if err != nil {
		return Manifest{}, fmt.Errorf("read manifest: %w", err)
	}
	return ParseManifest(data)
}

func WriteManifest(root string, manifest Manifest, opts WriteManifestOptions) error {
	data, err := MarshalManifest(manifest)
	if err != nil {
		return err
	}
	manifestPath := filepath.Join(root, ManifestName)
	if !opts.Overwrite {
		file, err := os.OpenFile(manifestPath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0o666)
		if err != nil {
			return fmt.Errorf("write manifest: %w", err)
		}
		if _, err := file.Write(data); err != nil {
			_ = file.Close()
			return fmt.Errorf("write manifest: %w", err)
		}
		if err := file.Close(); err != nil {
			return fmt.Errorf("write manifest: %w", err)
		}
		return nil
	}

	dir := root
	if dir == "" {
		dir = "."
	}
	tmp, err := os.CreateTemp(dir, ".manifest-*.tmp")
	if err != nil {
		return fmt.Errorf("write manifest temp: %w", err)
	}
	tmpPath := tmp.Name()
	cleanup := true
	defer func() {
		if cleanup {
			_ = os.Remove(tmpPath)
		}
	}()
	if _, err := tmp.Write(data); err != nil {
		_ = tmp.Close()
		return fmt.Errorf("write manifest temp: %w", err)
	}
	if err := tmp.Close(); err != nil {
		return fmt.Errorf("write manifest temp: %w", err)
	}
	if err := os.Rename(tmpPath, manifestPath); err != nil {
		return fmt.Errorf("replace manifest: %w", err)
	}
	cleanup = false
	return nil
}