// The file half of the client: what the agent may ask the editor to read and
// write for it, and how a mentioned file's text is fetched when a prompt is
// sent. The editor's own buffers are consulted first, so the agent sees what
// you can see rather than what was last saved.

package acp

import (
	"encoding/json"
	"errors"
	"os"

	"rickub.com/turbo-editors/turbo-core/jsonrpc"
)

// readFile returns a file's text as the editor sees it — the same view the
// agent gets from fs/read_text_file — falling back to the disk when the editor
// gave no way to ask it.
func (s *Session) readFile(path string) (string, error) {
	if s.options.ReadTextFile != nil {
		return s.options.ReadTextFile(path)
	}
	data, err := os.ReadFile(path)
	if err != nil {
		return "", err
	}
	return string(data), nil
}

// readTextFile answers with the text the editor sees, which is the buffer's
// when the file is open and modified.
func (s *Session) readTextFile(raw json.RawMessage) (any, error) {
	var params ReadTextFileParams
	if err := json.Unmarshal(raw, &params); err != nil {
		return nil, &jsonrpc.ResponseError{Code: jsonrpc.CodeInvalidParams, Message: err.Error()}
	}
	if s.options.ReadTextFile == nil {
		return nil, errors.New("this editor cannot read files for an agent")
	}

	content, err := s.options.ReadTextFile(params.Path)
	if err != nil {
		return nil, err
	}
	return ReadTextFileResult{Content: slice(content, params.Line, params.Limit)}, nil
}

// slice returns the lines the agent asked for, counting from one as the
// protocol does. Asking for neither gives the whole file.
func slice(content string, line, limit *int) string {
	if line == nil && limit == nil {
		return content
	}

	lines := splitLines(content)
	from := 0
	if line != nil && *line > 0 {
		from = min(*line-1, len(lines))
	}
	to := len(lines)
	if limit != nil && *limit >= 0 {
		to = min(from+*limit, len(lines))
	}
	return joinLines(lines[from:to])
}

// writeTextFile puts the agent's text where the editor can show it.
func (s *Session) writeTextFile(raw json.RawMessage) (any, error) {
	var params WriteTextFileParams
	if err := json.Unmarshal(raw, &params); err != nil {
		return nil, &jsonrpc.ResponseError{Code: jsonrpc.CodeInvalidParams, Message: err.Error()}
	}
	if s.options.WriteTextFile == nil {
		return nil, errors.New("this editor cannot write files for an agent")
	}
	if err := s.options.WriteTextFile(params.Path, params.Content); err != nil {
		return nil, err
	}
	return map[string]any{}, nil
}