+package main
+
+import (
+ "bytes"
+ "crypto/rand"
+ "encoding/hex"
+ "encoding/json"
+ "errors"
+ "fmt"
+ "io"
+ "os"
+ "path/filepath"
+ "strings"
+)
+
+const (
+ // instructionsFileName is the file of the user's instructions in the
+ // directory of an agent.
+ instructionsFileName = "instructions.md"
+
+ // agentIDBytes is the number of random bytes of an agent ID.
+ agentIDBytes = 16
+)
+
+// AgentConfig holds the settings of the config.json of an agent. ID is random,
+// made once when the file is made, and never changes. The cache key comes from
+// the ID, so a rename keeps the prompt cache and two agents with one name do
+// not share a key. Workdir is the directory where the commands of the agent
+// run.
+type AgentConfig struct {
+ Name string `json:"name"`
+ ID string `json:"id"`
+ Model string `json:"model"`
+ Effort string `json:"effort"`
+ Workdir string `json:"workdir"`
+}
+
+// Agent is one agent and its directory. The directory holds config.json, the
+// user's instructions in instructions.md, the chat, and the usage file.
+type Agent struct {
+ dir string
+ config AgentConfig
+}
+
+// openAgent reads the config.json of the agent in dir. When the file does not
+// exist, it makes the directory and writes the file with the defaults and a new
+// ID. A missing field of an existing file takes the default, but the ID must be
+// there. An unknown field is an error, so a typo does not become a silent
+// default.
+func openAgent(dir string) (*Agent, error) {
+ err := os.MkdirAll(dir, 0o700)
+ if err != nil {
+ return nil, fmt.Errorf("create agent directory: %w", err)
+ }
+
+ path := filepath.Join(dir, "config.json")
+ data, err := os.ReadFile(path)
+ if errors.Is(err, os.ErrNotExist) {
+ return createAgent(dir)
+ }
+
+ if err != nil {
+ return nil, fmt.Errorf("read agent config: %w", err)
+ }
+
+ config, err := defaultAgentConfig()
+ if err != nil {
+ return nil, err
+ }
+
+ decoder := json.NewDecoder(bytes.NewReader(data))
+ decoder.DisallowUnknownFields()
+ err = decoder.Decode(&config)
+ if err == nil && !errors.Is(decoder.Decode(&struct{}{}), io.EOF) {
+ err = errors.New("data after the JSON object")
+ }
+
+ if err == nil {
+ err = config.validate()
+ }
+
+ if err != nil {
+ return nil, fmt.Errorf("%s: %w", path, err)
+ }
+
+ return &Agent{
+ dir: dir,
+ config: config,
+ }, nil
+}
+
+// createAgent writes the config.json of a new agent in dir with the defaults
+// and a new ID.
+func createAgent(dir string) (*Agent, error) {
+ config, err := defaultAgentConfig()
+ if err != nil {
+ return nil, err
+ }
+
+ id := make([]byte, agentIDBytes)
+ _, err = rand.Read(id)
+ if err != nil {
+ return nil, fmt.Errorf("make agent ID: %w", err)
+ }
+
+ config.ID = hex.EncodeToString(id)
+ data, err := json.MarshalIndent(config, "", " ")
+ if err != nil {
+ return nil, fmt.Errorf("encode agent config: %w", err)
+ }
+
+ err = writeFileAtomic(filepath.Join(dir, "config.json"), append(data, '\n'))
+ if err != nil {
+ return nil, fmt.Errorf("write agent config: %w", err)
+ }
+
+ return &Agent{
+ dir: dir,
+ config: config,
+ }, nil
+}
+
+// defaultAgentConfig returns the settings of a new agent, without an ID. The
+// commands run in the home directory of the user.
+func defaultAgentConfig() (AgentConfig, error) {
+ home, err := os.UserHomeDir()
+ if err != nil {
+ return AgentConfig{}, fmt.Errorf("find working directory: %w", err)
+ }
+
+ return AgentConfig{
+ Name: "OneChat",
+ Model: "gpt-6.1-sol",
+ Effort: "medium",
+ Workdir: home,
+ }, nil
+}
+
+// validate makes sure that each setting has a valid value.
+func (c AgentConfig) validate() error {
+ if c.Name == "" || strings.ContainsAny(c.Name, "\r\n") {
+ return errors.New("name must be one line of text")
+ }
+
+ id, err := hex.DecodeString(c.ID)
+ if err != nil || len(id) != agentIDBytes {
+ return fmt.Errorf("id must be %d hexadecimal digits", 2*agentIDBytes)
+ }
+
+ if c.Model == "" || c.Effort == "" {
+ return errors.New("agent needs a model and an effort")
+ }
+
+ if !filepath.IsAbs(c.Workdir) {
+ return fmt.Errorf("workdir %q is not an absolute path", c.Workdir)
+ }
+
+ return nil
+}
+
+// CacheKey returns the prompt cache key of every model call of the agent.
+func (a *Agent) CacheKey() string {
+ return "onechat-" + a.config.ID
+}
+
+// Prompt returns the system prompt of the agent with the user's instructions
+// from instructions.md. It reads the file on each call, so a change applies at
+// the next call. A missing file means no instructions.
+func (a *Agent) Prompt() (string, error) {
+ data, err := os.ReadFile(filepath.Join(a.dir, instructionsFileName))
+ if err != nil && !errors.Is(err, os.ErrNotExist) {
+ return "", fmt.Errorf("read instructions: %w", err)
+ }
+
+ return prompt(a.config.Name, string(data)), nil
+}
projects / onechat / commitdiff