package nixstore

import (
	"encoding/base64"
	"fmt"
	"log"
	"net"
	"path"
	"strings"
	"sync"

	"hg.lukegb.com/lukegb/depot/go/nix/nar/narinfo"
	"hg.lukegb.com/lukegb/depot/go/nix/nixwire"
)

const (
	DaemonSock      = "/nix/var/nix/daemon-socket/socket"
	WorkerMagic1    = 0x6e697863
	WorkerMagic2    = 0x6478696f
	ProtocolVersion = 0x115

	WopQueryPathInfo              = 26
	WopQuerySubstitutablePathInfo = 21
)

type Daemon struct {
	conn net.Conn
	w    *nixwire.Serializer
	r    *nixwire.Deserializer
	mu   sync.Mutex
	err  error
}

func (d *Daemon) NARInfo(storePath string) (*narinfo.NarInfo, error) {
	d.mu.Lock()
	defer d.mu.Unlock()

	if _, err := d.w.WriteUint64(WopQueryPathInfo); err != nil {
		return nil, fmt.Errorf("writing worker op WopQueryPathInfo: %w", err)
	}
	if _, err := d.w.WriteString(storePath); err != nil {
		return nil, fmt.Errorf("writing store path query %v: %w", storePath, err)
	}

	if err := d.processStderr(); err != nil {
		return nil, fmt.Errorf("reading stderr from WopQueryPathInfo: %w", err)
	}

	validInt, err := d.r.ReadUint64()
	if err != nil {
		return nil, fmt.Errorf("reading path validity: %w", err)
	}
	valid := validInt == uint64(1)
	if !valid {
		return nil, fmt.Errorf("path %q is not valid", storePath)
	}

	ni := &narinfo.NarInfo{
		StorePath: storePath,
	}
	if ni.Deriver, err = d.r.ReadString(); err != nil {
		return nil, fmt.Errorf("reading deriver: %w", err)
	}
	ni.Deriver = path.Base(ni.Deriver)
	if ni.Deriver == "." {
		ni.Deriver = ""
	}

	hashStr, err := d.r.ReadString()
	if err != nil {
		return nil, fmt.Errorf("reading NAR hash: %w", err)
	}
	if ni.NarHash, err = narinfo.HashFromString("sha256:" + hashStr); err != nil {
		return nil, fmt.Errorf("parsing NAR hash %q: %w", hashStr, err)
	}

	refs, err := d.r.ReadStrings()
	if err != nil {
		return nil, fmt.Errorf("reading referrers: %w", err)
	}
	for n, ref := range refs {
		refs[n] = path.Base(ref)
	}
	ni.References = refs

	if _, err := d.r.ReadUint64(); err != nil {
		return nil, fmt.Errorf("reading registration time: %w", err)
	}
	if ni.NarSize, err = d.r.ReadUint64(); err != nil {
		return nil, fmt.Errorf("reading narsize: %w", err)
	}
	if _, err := d.r.ReadUint64(); err != nil {
		return nil, fmt.Errorf("reading ultimate: %w", err)
	}
	sigs, err := d.r.ReadStrings()
	if err != nil {
		return nil, fmt.Errorf("reading sigs: %w", err)
	}
	if _, err := d.r.ReadUint64(); err != nil {
		return nil, fmt.Errorf("reading CA: %w", err)
	}

	ni.Sig = make(map[string][]byte)
	for _, sigStr := range sigs {
		sigBits := strings.Split(sigStr, ":")
		sigHash, err := base64.StdEncoding.DecodeString(sigBits[1])
		if err != nil {
			return nil, fmt.Errorf("decoding signature %q: %w", sigStr, err)
		}
		ni.Sig[sigBits[0]] = sigHash
	}

	return ni, nil
}

func (d *Daemon) Close() error {
	d.mu.Lock()
	defer d.mu.Unlock()

	return d.conn.Close()
}

func (d *Daemon) readFields() ([]any, error) {
	fieldsSz, err := d.r.ReadUint64()
	if err != nil {
		return nil, fmt.Errorf("reading fields count: %w", err)
	}
	var fields []any
	for n := 0; n < int(fieldsSz); n++ {
		fieldTyp, err := d.r.ReadUint64()
		if err != nil {
			return nil, fmt.Errorf("reading field %d type: %w", n, err)
		}
		switch fieldTyp {
		case 0: // tInt
			fieldVal, err := d.r.ReadUint64()
			if err != nil {
				return nil, fmt.Errorf("reading field %d int: %w", n, err)
			}
			fields = append(fields, fieldVal)
		case 1: // tString
			fieldVal, err := d.r.ReadString()
			if err != nil {
				return nil, fmt.Errorf("reading field %d str: %w", n, err)
			}
			fields = append(fields, fieldVal)
		default:
			return nil, fmt.Errorf("reading field %d: unsupported field type %x", n, fieldTyp)
		}
	}
	return fields, nil
}

func (d *Daemon) processStderr() error {
	for {
		msg, err := d.r.ReadUint64()
		if err != nil {
			return fmt.Errorf("read stderr msg code: %w", err)
		}
		switch msg {
		case 0x64617416: // STDERR_WRITE
			stderr, err := d.r.ReadString()
			if err != nil {
				return fmt.Errorf("read stderr msg: %w", err)
			}
			log.Println(stderr)
		case 0x64617461: // STDERR_READ
			return fmt.Errorf("STDERR_READ requested")
		case 0x63787470: // STDERR_ERROR
			errStr, err := d.r.ReadString()
			if err != nil {
				return fmt.Errorf("STDERR_ERROR reading error string: %w", err)
			}
			status, err := d.r.ReadUint64()
			if err != nil {
				return fmt.Errorf("STDERR_ERROR reading uint64: %w", err)
			}
			return fmt.Errorf("error code %d: %v", status, errStr)
		case 0x6f6c6d67: // STDERR_NEXT
			errStr, err := d.r.ReadString()
			if err != nil {
				return fmt.Errorf("STDERR_NEXT reading error string: %w", err)
			}
			return fmt.Errorf("error: %v", errStr)
		case 0x53545254: // STDERR_START_ACTIVITY
			activity, err := d.r.ReadUint64()
			if err != nil {
				return fmt.Errorf("STDERR_START_ACTIVITY reading ActivityId: %w", err)
			}
			lvl, err := d.r.ReadUint64()
			if err != nil {
				return fmt.Errorf("STDERR_START_ACTIVITY reading level: %w", err)
			}
			actType, err := d.r.ReadUint64()
			if err != nil {
				return fmt.Errorf("STDERR_START_ACTIVITY reading activity type: %w", err)
			}
			s, err := d.r.ReadString()
			if err != nil {
				return fmt.Errorf("STDERR_START_ACTIVITY reading s: %w", err)
			}
			fields, err := d.readFields()
			if err != nil {
				return fmt.Errorf("STDERR_START_ACTIVITY fields: %w", err)
			}
			parentActivity, err := d.r.ReadUint64()
			if err != nil {
				return fmt.Errorf("STDERR_START_ACTIVITY reading parent activity: %w", err)
			}
			log.Printf("START_ACTIVITY activity=%d, lvl=%d, actType=%d, s=%s, fields=%v, parentActivity=%d", activity, lvl, actType, s, fields, parentActivity)
		case 0x53544f50: // STDERR_STOP_ACTIVITY
			activity, err := d.r.ReadUint64()
			if err != nil {
				return fmt.Errorf("STDERR_STOP_ACTIVITY reading ActivityId: %w", err)
			}
			log.Printf("STOP_ACTIVITY activity=%d", activity)
		case 0x52534c54: // STDERR_RESULT
			activity, err := d.r.ReadUint64()
			if err != nil {
				return fmt.Errorf("STDERR_RESULT reading ActivityId: %w", err)
			}
			resultTyp, err := d.r.ReadUint64()
			if err != nil {
				return fmt.Errorf("STDERR_RESULT reading result: %w", err)
			}
			fields, err := d.readFields()
			if err != nil {
				return fmt.Errorf("STDERR_RESULT fields: %w", err)
			}
			log.Printf("activity RESULT activity=%d resultType=%d fields=%v", activity, resultTyp, fields)
		case 0x616c7473: // STDERR_LAST
			return nil
		}
	}
}

func (d *Daemon) hello() error {
	_, err := d.w.WriteUint64(WorkerMagic1)
	if err != nil {
		return fmt.Errorf("writing magic 1: %w", err)
	}

	magic2, err := d.r.ReadUint64()
	if err != nil {
		return fmt.Errorf("reading magic 2: %w", err)
	}
	if magic2 != WorkerMagic2 {
		return fmt.Errorf("magic 2 mismatch: got %x, wanted %x", magic2, WorkerMagic2)
	}

	daemonVersion, err := d.r.ReadUint64()
	if err != nil {
		return fmt.Errorf("reading daemon version: %w", err)
	}
	majorVersion := int((daemonVersion >> 8) & 0xff)
	minorVersion := int(daemonVersion & 0xff)
	if majorVersion != 1 {
		return fmt.Errorf("daemon major version mismatch: got %d, want 1", majorVersion)
	}
	if minorVersion < 21 {
		return fmt.Errorf("daemon minor version too old: got %d, want at least 21", minorVersion)
	}

	if _, err := d.w.WriteUint64(ProtocolVersion); err != nil {
		return fmt.Errorf("writing protocol version: %w", err)
	}

	if _, err := d.w.WriteUint64(0); err != nil {
		return fmt.Errorf("writing obsolete CPU affinity: %w", err)
	}
	if _, err := d.w.WriteUint64(0); err != nil {
		return fmt.Errorf("writing obsolete reserveSpace: %w", err)
	}

	return d.processStderr()
}

func OpenDaemon(path string) (*Daemon, error) {
	conn, err := net.Dial("unix", path)
	if err != nil {
		return nil, fmt.Errorf("dialing %v: %w", path, err)
	}

	d := &Daemon{conn: conn, w: &nixwire.Serializer{conn}, r: &nixwire.Deserializer{conn}}
	if err := d.hello(); err != nil {
		d.Close()
		return nil, fmt.Errorf("sending hello to %v: %w", path, err)
	}

	// /nix/var/nix/daemon-socket/socket
	return d, nil
}