package database

import (
	"bytes"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"

	"git.sr.ht/~emersion/drmdb/drmtree"
)

const Dir = "db"

var ErrStop = fmt.Errorf("drmdb: stop walking")

func generateKey(n *drmtree.Node) (string, error) {
	if n.Driver == nil || n.Device == nil {
		return "", fmt.Errorf("node is missing driver/device")
	}

	ver := &n.Driver.Version

	var b bytes.Buffer
	b.WriteString(n.Driver.Name)
	b.WriteByte(0)
	fmt.Fprintf(&b, "%v.%v.%v-%v", ver.Major, ver.Minor, ver.Patch, ver.Date)
	b.WriteByte(0)
	b.WriteString(n.Driver.Kernel.SysName)
	b.WriteByte(0)
	b.WriteString(n.Driver.Kernel.Release)
	b.WriteByte(0)
	switch dev := n.Device.DeviceData.(type) {
	case *drmtree.DevicePCI:
		b.WriteString("pci")
		b.WriteByte(0)
		fmt.Fprintf(&b, "%04X:%04X", dev.Vendor, dev.Device)
	case *drmtree.DevicePlatform:
		b.WriteString("platform")
		if len(dev.Compatible) == 0 {
			return "", fmt.Errorf("platform device is missing compatibility info")
		}
		for _, compat := range dev.Compatible {
			b.WriteByte(0)
			b.WriteString(compat)
		}
	default:
		return "", fmt.Errorf("device bus type %v not supported", n.Device.BusType)
	}

	sum := sha256.Sum256(b.Bytes())
	return hex.EncodeToString(sum[:])[:12], nil
}

func initDB() error {
	return os.MkdirAll(Dir, 0755)
}

func store(n *drmtree.Node) (string, error) {
	k, err := generateKey(n)
	if err != nil {
		return "", err
	}

	p := filepath.Join(Dir, k+".json")
	f, err := os.OpenFile(p, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0666)
	if err != nil {
		if os.IsExist(err) {
			return "", fmt.Errorf("data has already been submitted")
		}
		return "", err
	}
	defer f.Close()

	if err := json.NewEncoder(f).Encode(n); err != nil {
		return "", err
	}

	return k, f.Close()
}

func load(k string) (*drmtree.Node, error) {
	p := filepath.Join(Dir, k+".json")
	f, err := os.Open(p)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	var n drmtree.Node
	if err := json.NewDecoder(f).Decode(&n); err != nil {
		return nil, err
	}

	return &n, f.Close()
}

func walk(fn func(k string) error) error {
	files, err := ioutil.ReadDir(Dir)
	if err != nil {
		return err
	}

	for _, fi := range files {
		if !strings.HasSuffix(fi.Name(), ".json") {
			continue
		}
		k := strings.TrimSuffix(fi.Name(), ".json")

		if err := fn(k); err == ErrStop {
			return nil
		} else if err != nil {
			return err
		}
	}

	return nil
}