package agent

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	acp "github.com/coder/acp-go-sdk"
)

// client implements acp.Client: the callbacks the agent invokes on us.
// Session updates and permission requests are delegated to the Handler; file
// system access is served directly; terminals are not supported in this
// version, matching the capabilities announced during initialize.
type client struct {
	handler Handler
}

var _ acp.Client = (*client)(nil)

func (c *client) SessionUpdate(ctx context.Context, params acp.SessionNotification) error {
	c.handler.HandleSessionUpdate(ctx, params)
	return nil
}

func (c *client) RequestPermission(ctx context.Context, params acp.RequestPermissionRequest) (acp.RequestPermissionResponse, error) {
	return c.handler.HandlePermissionRequest(ctx, params)
}

func (c *client) ReadTextFile(_ context.Context, params acp.ReadTextFileRequest) (acp.ReadTextFileResponse, error) {
	if !filepath.IsAbs(params.Path) {
		return acp.ReadTextFileResponse{}, fmt.Errorf("path must be absolute: %s", params.Path)
	}
	raw, err := os.ReadFile(params.Path)
	if err != nil {
		return acp.ReadTextFileResponse{}, fmt.Errorf("read %s: %w", params.Path, err)
	}
	return acp.ReadTextFileResponse{Content: sliceLines(string(raw), params.Line, params.Limit)}, nil
}

func (c *client) WriteTextFile(_ context.Context, params acp.WriteTextFileRequest) (acp.WriteTextFileResponse, error) {
	if !filepath.IsAbs(params.Path) {
		return acp.WriteTextFileResponse{}, fmt.Errorf("path must be absolute: %s", params.Path)
	}
	if dir := filepath.Dir(params.Path); dir != "" {
		if err := os.MkdirAll(dir, 0o755); err != nil {
			return acp.WriteTextFileResponse{}, fmt.Errorf("mkdir %s: %w", dir, err)
		}
	}
	if err := os.WriteFile(params.Path, []byte(params.Content), 0o644); err != nil {
		return acp.WriteTextFileResponse{}, fmt.Errorf("write %s: %w", params.Path, err)
	}
	return acp.WriteTextFileResponse{}, nil
}

// sliceLines applies ACP's optional 1-based line offset and line count to a
// file's content.
func sliceLines(content string, line, limit *int) string {
	if line == nil && limit == nil {
		return content
	}
	lines := strings.Split(content, "\n")
	start := 0
	if line != nil && *line > 0 {
		start = min(*line-1, len(lines))
	}
	end := len(lines)
	if limit != nil && *limit > 0 && start+*limit < end {
		end = start + *limit
	}
	return strings.Join(lines[start:end], "\n")
}

// Terminal support is announced as absent during initialize; a conforming
// agent never calls these. They still answer with a proper JSON-RPC error
// instead of panicking on a non-conforming one.

func (c *client) CreateTerminal(context.Context, acp.CreateTerminalRequest) (acp.CreateTerminalResponse, error) {
	return acp.CreateTerminalResponse{}, acp.NewMethodNotFound(acp.ClientMethodTerminalCreate)
}

func (c *client) KillTerminal(context.Context, acp.KillTerminalRequest) (acp.KillTerminalResponse, error) {
	return acp.KillTerminalResponse{}, acp.NewMethodNotFound(acp.ClientMethodTerminalKill)
}

func (c *client) TerminalOutput(context.Context, acp.TerminalOutputRequest) (acp.TerminalOutputResponse, error) {
	return acp.TerminalOutputResponse{}, acp.NewMethodNotFound(acp.ClientMethodTerminalOutput)
}

func (c *client) ReleaseTerminal(context.Context, acp.ReleaseTerminalRequest) (acp.ReleaseTerminalResponse, error) {
	return acp.ReleaseTerminalResponse{}, acp.NewMethodNotFound(acp.ClientMethodTerminalRelease)
}

func (c *client) WaitForTerminalExit(context.Context, acp.WaitForTerminalExitRequest) (acp.WaitForTerminalExitResponse, error) {
	return acp.WaitForTerminalExitResponse{}, acp.NewMethodNotFound(acp.ClientMethodTerminalWaitForExit)
}