// Copyright 2026 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package envcheck

import (
	"context"
	"encoding/json"
	"os/exec"
	"runtime"
	"strings"
	"time"

	"github.com/docker/docker/client"
)

// RunnerCapabilities represents the capabilities of a runner for AI consumption
type RunnerCapabilities struct {
	OS               string              `json:"os"`
	Arch             string              `json:"arch"`
	Docker           bool                `json:"docker"`
	DockerCompose    bool                `json:"docker_compose"`
	ContainerRuntime string              `json:"container_runtime,omitempty"`
	Shell            []string            `json:"shell,omitempty"`
	Tools            map[string][]string `json:"tools,omitempty"`
	Features         *CapabilityFeatures `json:"features,omitempty"`
	Limitations      []string            `json:"limitations,omitempty"`
}

// CapabilityFeatures represents feature support flags
type CapabilityFeatures struct {
	ArtifactsV4      bool `json:"artifacts_v4"`
	Cache            bool `json:"cache"`
	Services         bool `json:"services"`
	CompositeActions bool `json:"composite_actions"`
}

// DetectCapabilities detects the runner's capabilities
func DetectCapabilities(ctx context.Context, dockerHost string) *RunnerCapabilities {
	cap := &RunnerCapabilities{
		OS:     runtime.GOOS,
		Arch:   runtime.GOARCH,
		Tools:  make(map[string][]string),
		Shell:  detectShells(),
		Features: &CapabilityFeatures{
			ArtifactsV4:      false, // Gitea doesn't support v4 artifacts
			Cache:            true,
			Services:         true,
			CompositeActions: true,
		},
		Limitations: []string{
			"actions/upload-artifact@v4 not supported (use v3 or direct API upload)",
			"actions/download-artifact@v4 not supported (use v3)",
		},
	}

	// Detect Docker
	cap.Docker, cap.ContainerRuntime = detectDocker(ctx, dockerHost)
	if cap.Docker {
		cap.DockerCompose = detectDockerCompose(ctx)
		cap.Features.Services = true
	}

	// Detect common tools
	detectTools(ctx, cap)

	return cap
}

// ToJSON converts capabilities to JSON string for transmission
func (c *RunnerCapabilities) ToJSON() string {
	data, err := json.Marshal(c)
	if err != nil {
		return "{}"
	}
	return string(data)
}

func detectShells() []string {
	shells := []string{}

	switch runtime.GOOS {
	case "windows":
		if _, err := exec.LookPath("pwsh"); err == nil {
			shells = append(shells, "pwsh")
		}
		if _, err := exec.LookPath("powershell"); err == nil {
			shells = append(shells, "powershell")
		}
		shells = append(shells, "cmd")
	case "darwin":
		if _, err := exec.LookPath("zsh"); err == nil {
			shells = append(shells, "zsh")
		}
		if _, err := exec.LookPath("bash"); err == nil {
			shells = append(shells, "bash")
		}
		shells = append(shells, "sh")
	default: // linux and others
		if _, err := exec.LookPath("bash"); err == nil {
			shells = append(shells, "bash")
		}
		shells = append(shells, "sh")
	}

	return shells
}

func detectDocker(ctx context.Context, dockerHost string) (bool, string) {
	opts := []client.Opt{client.FromEnv}
	if dockerHost != "" {
		opts = append(opts, client.WithHost(dockerHost))
	}

	cli, err := client.NewClientWithOpts(opts...)
	if err != nil {
		return false, ""
	}
	defer cli.Close()

	timeoutCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()

	_, err = cli.Ping(timeoutCtx)
	if err != nil {
		return false, ""
	}

	// Check if it's podman or docker
	info, err := cli.Info(timeoutCtx)
	if err == nil {
		if strings.Contains(strings.ToLower(info.Name), "podman") {
			return true, "podman"
		}
	}

	return true, "docker"
}

func detectDockerCompose(ctx context.Context) bool {
	// Check for docker compose v2 (docker compose)
	cmd := exec.CommandContext(ctx, "docker", "compose", "version")
	if err := cmd.Run(); err == nil {
		return true
	}

	// Check for docker-compose v1
	if _, err := exec.LookPath("docker-compose"); err == nil {
		return true
	}

	return false
}

func detectTools(ctx context.Context, cap *RunnerCapabilities) {
	toolDetectors := map[string]func(context.Context) []string{
		"node":   detectNodeVersions,
		"go":     detectGoVersions,
		"python": detectPythonVersions,
		"java":   detectJavaVersions,
		"dotnet": detectDotnetVersions,
		"rust":   detectRustVersions,
	}

	for tool, detector := range toolDetectors {
		if versions := detector(ctx); len(versions) > 0 {
			cap.Tools[tool] = versions
		}
	}
}

func detectNodeVersions(ctx context.Context) []string {
	return detectToolVersion(ctx, "node", "--version", "v")
}

func detectGoVersions(ctx context.Context) []string {
	return detectToolVersion(ctx, "go", "version", "go")
}

func detectPythonVersions(ctx context.Context) []string {
	versions := []string{}

	// Try python3 first
	if v := detectToolVersion(ctx, "python3", "--version", "Python "); len(v) > 0 {
		versions = append(versions, v...)
	}

	// Also try python
	if v := detectToolVersion(ctx, "python", "--version", "Python "); len(v) > 0 {
		// Avoid duplicates
		for _, ver := range v {
			found := false
			for _, existing := range versions {
				if existing == ver {
					found = true
					break
				}
			}
			if !found {
				versions = append(versions, ver)
			}
		}
	}

	return versions
}

func detectJavaVersions(ctx context.Context) []string {
	cmd := exec.CommandContext(ctx, "java", "-version")
	output, err := cmd.CombinedOutput()
	if err != nil {
		return nil
	}

	// Java version output goes to stderr and looks like: openjdk version "17.0.1" or java version "1.8.0_301"
	lines := strings.Split(string(output), "\n")
	for _, line := range lines {
		if strings.Contains(line, "version") {
			// Extract version from quotes
			start := strings.Index(line, "\"")
			end := strings.LastIndex(line, "\"")
			if start != -1 && end > start {
				version := line[start+1 : end]
				// Simplify version (e.g., "17.0.1" -> "17")
				parts := strings.Split(version, ".")
				if len(parts) > 0 {
					if parts[0] == "1" && len(parts) > 1 {
						return []string{parts[1]} // Java 8 style: 1.8 -> 8
					}
					return []string{parts[0]}
				}
			}
		}
	}

	return nil
}

func detectDotnetVersions(ctx context.Context) []string {
	cmd := exec.CommandContext(ctx, "dotnet", "--list-sdks")
	output, err := cmd.Output()
	if err != nil {
		return nil
	}

	versions := []string{}
	lines := strings.Split(string(output), "\n")
	for _, line := range lines {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		// Format: "8.0.100 [/path/to/sdk]"
		parts := strings.Split(line, " ")
		if len(parts) > 0 {
			version := parts[0]
			// Simplify to major version
			major := strings.Split(version, ".")[0]
			// Avoid duplicates
			found := false
			for _, v := range versions {
				if v == major {
					found = true
					break
				}
			}
			if !found {
				versions = append(versions, major)
			}
		}
	}

	return versions
}

func detectRustVersions(ctx context.Context) []string {
	return detectToolVersion(ctx, "rustc", "--version", "rustc ")
}

func detectToolVersion(ctx context.Context, cmd string, args string, prefix string) []string {
	timeoutCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()

	c := exec.CommandContext(timeoutCtx, cmd, args)
	output, err := c.Output()
	if err != nil {
		return nil
	}

	line := strings.TrimSpace(string(output))
	if prefix != "" {
		if idx := strings.Index(line, prefix); idx != -1 {
			line = line[idx+len(prefix):]
		}
	}

	// Get just the version number
	parts := strings.Fields(line)
	if len(parts) > 0 {
		version := parts[0]
		// Clean up version string
		version = strings.TrimPrefix(version, "v")
		// Return major.minor or just major
		vparts := strings.Split(version, ".")
		if len(vparts) >= 2 {
			return []string{vparts[0] + "." + vparts[1]}
		}
		return []string{vparts[0]}
	}

	return nil
}