package main

import (
	"bufio"
	"crypto/subtle"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"net/http"
	"os"
	"os/exec"
	"regexp"
	"strings"
	"sync"
	"time"
)

const maxLogLines = 400

var tagPattern = regexp.MustCompile(`^v\d+\.\d+\.\d+$`)

type releaseRequest struct {
	Tag       string `json:"tag"`
	Notes     string `json:"notes"`
	Mandatory bool   `json:"mandatory"`
}

type releaseStatus struct {
	State      string    `json:"state"`
	Tag        string    `json:"tag,omitempty"`
	Mandatory  bool      `json:"mandatory"`
	StartedAt  time.Time `json:"startedAt,omitempty"`
	FinishedAt time.Time `json:"finishedAt,omitempty"`
	Message    string    `json:"message,omitempty"`
	Logs       []string  `json:"logs"`
	Fallback   string    `json:"fallback"`
}

type controller struct {
	mu     sync.RWMutex
	status releaseStatus
	token  []byte
}

func main() {
	token, err := readSecret("/run/secrets/memby_release_publish_token")
	if err != nil {
		log.Fatal(err)
	}
	c := &controller{token: token, status: releaseStatus{
		State: "idle", Logs: []string{},
		Fallback: "docker compose run --rm --build memby-builder release",
	}}
	mux := http.NewServeMux()
	mux.HandleFunc("GET /healthz", func(w http.ResponseWriter, _ *http.Request) { w.WriteHeader(http.StatusNoContent) })
	mux.Handle("GET /v1/status", c.authorise(http.HandlerFunc(c.handleStatus)))
	mux.Handle("POST /v1/releases", c.authorise(http.HandlerFunc(c.handleRelease)))
	server := &http.Server{Addr: ":8090", Handler: mux, ReadHeaderTimeout: 5 * time.Second, IdleTimeout: 30 * time.Second}
	log.Printf("Memby release controller listening on %s", server.Addr)
	log.Fatal(server.ListenAndServe())
}

func readSecret(path string) ([]byte, error) {
	value, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("release controller token: %w", err)
	}
	value = []byte(strings.TrimSpace(string(value)))
	if len(value) == 0 {
		return nil, errors.New("release controller token is empty")
	}
	return value, nil
}

func (c *controller) authorise(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		presented := strings.TrimSpace(strings.TrimPrefix(r.Header.Get("Authorization"), "Bearer "))
		if subtle.ConstantTimeCompare([]byte(presented), c.token) != 1 {
			writeError(w, http.StatusUnauthorized, "invalid release token")
			return
		}
		next.ServeHTTP(w, r)
	})
}

func (c *controller) handleStatus(w http.ResponseWriter, _ *http.Request) {
	c.mu.RLock()
	status := c.status
	// Start with a non-nil slice so an idle controller emits `[]`, not `null`. The Admin
	// Console is still defensive for compatibility with already-deployed controllers.
	status.Logs = append([]string{}, c.status.Logs...)
	c.mu.RUnlock()
	writeJSON(w, http.StatusOK, status)
}

func (c *controller) handleRelease(w http.ResponseWriter, r *http.Request) {
	r.Body = http.MaxBytesReader(w, r.Body, 16<<10)
	var request releaseRequest
	decoder := json.NewDecoder(r.Body)
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&request); err != nil {
		writeError(w, http.StatusBadRequest, "invalid release request")
		return
	}
	request.Tag = strings.TrimSpace(request.Tag)
	request.Notes = strings.TrimSpace(request.Notes)
	if request.Tag != "" && !tagPattern.MatchString(request.Tag) {
		writeError(w, http.StatusBadRequest, "tag must be blank or look like v0.2.64")
		return
	}
	if len(request.Notes) > 4000 {
		writeError(w, http.StatusBadRequest, "release notes are too long")
		return
	}
	c.mu.Lock()
	if c.status.State == "running" {
		c.mu.Unlock()
		writeError(w, http.StatusConflict, "a Memby release is already running")
		return
	}
	c.status = releaseStatus{
		State: "running", Tag: request.Tag, Mandatory: request.Mandatory,
		StartedAt: time.Now().UTC(), Message: "Preparing the Android release builder", Logs: []string{},
		Fallback: "docker compose run --rm --build memby-builder release",
	}
	status := c.status
	c.mu.Unlock()
	go c.run(request)
	writeJSON(w, http.StatusAccepted, status)
}

func (c *controller) run(request releaseRequest) {
	command := exec.Command("/usr/local/bin/memby-builder", "release")
	command.Env = append(os.Environ(),
		"MEMBY_RELEASE_TAG="+request.Tag,
		"MEMBY_RELEASE_NOTES="+request.Notes,
		fmt.Sprintf("MEMBY_RELEASE_MANDATORY=%t", request.Mandatory),
	)
	stdout, err := command.StdoutPipe()
	if err != nil {
		c.finish(err)
		return
	}
	command.Stderr = command.Stdout
	if err := command.Start(); err != nil {
		c.finish(err)
		return
	}
	done := make(chan struct{})
	go func() {
		scanner := bufio.NewScanner(stdout)
		scanner.Buffer(make([]byte, 64*1024), 1024*1024)
		for scanner.Scan() {
			c.appendLog(scanner.Text())
		}
		if err := scanner.Err(); err != nil {
			c.appendLog("Could not read complete build output: " + err.Error())
		}
		close(done)
	}()
	err = command.Wait()
	<-done
	c.finish(err)
}

func (c *controller) appendLog(line string) {
	c.mu.Lock()
	defer c.mu.Unlock()
	line = strings.TrimSpace(line)
	if line == "" {
		return
	}
	c.status.Logs = append(c.status.Logs, line)
	if len(c.status.Logs) > maxLogLines {
		c.status.Logs = append([]string(nil), c.status.Logs[len(c.status.Logs)-maxLogLines:]...)
	}
	c.status.Message = line
}

func (c *controller) finish(err error) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.status.FinishedAt = time.Now().UTC()
	if err != nil {
		c.status.State = "failed"
		c.status.Message = "Release failed: " + err.Error()
		return
	}
	c.status.State = "succeeded"
	c.status.Message = "Release built, verified and published"
}

func writeJSON(w http.ResponseWriter, status int, value any) {
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Cache-Control", "no-store")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(value)
}

func writeError(w http.ResponseWriter, status int, message string) {
	writeJSON(w, status, map[string]string{"error": message})
}