package compose

import (
	"context"
	"encoding/json"
	"fmt"
	"os/exec"
	"strings"
	"time"
)

// dockerBin is the Docker CLI binary name. Overridable in tests via
// SetDockerBin so the management/discovery code never hard-codes a path.
var dockerBin = "docker"

// SetDockerBin overrides the Docker CLI binary used by discovery and
// management. Pass an empty value to restore the default ("docker").
// Tests use it to point at a stub binary; production leaves it alone.
func SetDockerBin(name string) {
	if name == "" {
		dockerBin = "docker"
		return
	}
	dockerBin = name
}

// commandTimeout is the deadline applied to every Docker CLI call so a
// hung dockerd cannot wedge the inventory refresh loop or a management
// request. 30s is well above `docker ps` / `docker inspect` on a busy
// host but short enough that the operator notices.
const commandTimeout = 30 * time.Second

// Available reports whether the Docker CLI can reach the daemon. Used
// by the refresh loop to no-op (instead of erroring) on hosts without
// Docker, and by the UI to show a "Docker not available" banner.
func Available(ctx context.Context) bool {
	c, cancel := context.WithTimeout(ctx, commandTimeout)
	defer cancel()
	if err := exec.CommandContext(c, dockerBin, "version").Run(); err != nil {
		return false
	}
	// `docker version` succeeds against the client even when the daemon
	// is down on some builds; `docker ps` requires the daemon, so it is
	// the authoritative liveness probe.
	pc, pcancel := context.WithTimeout(ctx, commandTimeout)
	defer pcancel()
	return exec.CommandContext(pc, dockerBin, "ps", "--format", "{{.ID}}").Run() == nil
}

// composeLSItem is one row of `docker compose ls --all --format json`.
type composeLSItem struct {
	Name        string `json:"Name"`
	Status      string `json:"Status"`
	ConfigFiles string `json:"ConfigFiles"`
}

// composeLS runs `docker compose ls --all --format json` and returns
// the projects keyed by name. Unlike `docker ps --format json` (NDJSON),
// `docker compose ls` emits a single JSON array, so the whole stdout is
// unmarshalled at once. Non-fatal: returns an empty map on any error.
func composeLS(ctx context.Context) map[string]composeLSItem {
	out, err := runDocker(ctx, "compose", "ls", "--all", "--format", "json")
	if err != nil {
		return nil
	}
	trimmed := strings.TrimSpace(out)
	if trimmed == "" {
		return nil
	}
	var items []composeLSItem
	if err := json.Unmarshal([]byte(trimmed), &items); err != nil {
		return nil
	}
	m := make(map[string]composeLSItem, len(items))
	for _, it := range items {
		m[it.Name] = it
	}
	return m
}

// runDocker executes the Docker CLI with the given args and returns
// stdout. The context deadline is enforced by Go (CommandContext); a
// non-zero exit yields an error that carries the daemon's stderr so the
// caller can surface the daemon's diagnostic instead of a bare exit code.
func runDocker(ctx context.Context, args ...string) (string, error) {
	c, cancel := context.WithTimeout(ctx, commandTimeout)
	defer cancel()
	cmd := exec.CommandContext(c, dockerBin, args...)
	out, err := cmd.Output()
	if err != nil {
		if ee, ok := err.(*exec.ExitError); ok && len(ee.Stderr) > 0 {
			return "", fmt.Errorf("%s: %s", strings.Join(args, " "), strings.TrimSpace(string(ee.Stderr)))
		}
		return "", err
	}
	return string(out), nil
}

// dockerCombined runs the Docker CLI with a working directory and
// returns combined stdout+stderr. Used by management operations, which
// must run inside the project's working directory so Compose resolves
// the compose file and `.env` exactly as the operator would. Unlike
// runDocker, stderr is merged into the returned string because compose
// progress output goes to stderr and is useful to the operator.
func dockerCombined(ctx context.Context, dir string, args ...string) (string, error) {
	c, cancel := context.WithTimeout(ctx, commandTimeout)
	defer cancel()
	cmd := exec.CommandContext(c, dockerBin, args...)
	cmd.Dir = dir
	out, err := cmd.CombinedOutput()
	return string(out), err
}

// parseLabels parses the comma-separated `key=value` label string that
// `docker ps --format json` emits in the Labels field. Tolerates empty
// input and values containing '=' (only the first '=' splits).
func parseLabels(labels string) map[string]string {
	out := make(map[string]string)
	if labels == "" {
		return out
	}
	for _, pair := range strings.Split(labels, ",") {
		k, v, ok := strings.Cut(pair, "=")
		if !ok {
			continue
		}
		out[strings.TrimSpace(k)] = strings.TrimSpace(v)
	}
	return out
}