feat: support two types of role prompts (#52)

1. embeded prompt

use __INPUT__ placeholder
will generate one user message when send to gpt
```
- name: shell
  prompt: >
    I want you to act as a linux shell expert.
    Q: How to unzip a file
    A: unzip file.zip
    Q: __INPUT__
    A:
```

2. system prompt
no __INPUT__ placeholder
will generate on system message and one user message when send to gpt
```
- name: shell
  prompt: |
    I want you to act as a linux shell expert.
    I want you to answer only with bash code.
    Do not write explanations.
```

4 files changed, 192 insertions, 103 deletions

diff --git a/src/config/conversation.rs b/src/config/conversation.rs
index 23eacb5..c3e9bed 100644
--- a/src/config/conversation.rs
+++ b/src/config/conversation.rs
@@ -1,93 +1,81 @@
-use anyhow::Result;
-use serde::{Deserialize, Serialize};
-use serde_json::{json, Value};
+use super::message::{Message, MessageRole, MESSAGE_EXTRA_TOKENS};
+use super::role::Role;
+use super::MAX_TOKENS;
 
 use crate::utils::count_tokens;
 
-use super::{MAX_TOKENS, MESSAGE_EXTRA_TOKENS};
+use anyhow::Result;
+use serde::{Deserialize, Serialize};
 
 #[derive(Debug, Clone, Deserialize, Serialize)]
 pub struct Conversation {
     pub tokens: usize,
+    pub role: Option<Role>,
     pub messages: Vec<Message>,
 }
 
-#[derive(Debug, Clone, Deserialize, Serialize)]
-pub struct Message {
-    pub role: MessageRole,
-    pub content: String,
-}
-
 impl Conversation {
-    pub fn new() -> Self {
+    pub fn new(role: Option<Role>) -> Self {
+        let tokens = if let Some(role) = role.as_ref() {
+            role.consume_tokens()
+        } else {
+            0
+        };
         Self {
-            tokens: 0,
+            tokens,
+            role,
             messages: vec![],
         }
     }
 
-    pub fn add_chat(&mut self, input: &str, output: &str) -> Result<()> {
-        self.messages.push(Message {
-            role: MessageRole::User,
-            content: input.to_string(),
-        });
+    pub fn add_message(&mut self, input: &str, output: &str) -> Result<()> {
+        let mut need_add_msg = true;
+        let mut input_tokens = count_tokens(input);
+        if self.messages.is_empty() {
+            if let Some(role) = self.role.as_ref() {
+                self.messages.extend(role.build_emssages(input));
+                need_add_msg = false;
+            }
+        }
+        if need_add_msg {
+            self.messages.push(Message {
+                role: MessageRole::User,
+                content: input.to_string(),
+            });
+            input_tokens += MESSAGE_EXTRA_TOKENS;
+        }
         self.messages.push(Message {
             role: MessageRole::Assistant,
             content: output.to_string(),
         });
-        self.tokens += count_tokens(input) + count_tokens(output) + 2 * MESSAGE_EXTRA_TOKENS;
+        self.tokens += input_tokens + count_tokens(output) + MESSAGE_EXTRA_TOKENS;
         Ok(())
     }
 
-    /// Readline prompt
-    pub fn add_prompt(&mut self, prompt: &str) {
-        self.messages.push(Message {
-            role: MessageRole::System,
-            content: prompt.into(),
-        });
-        self.tokens += count_tokens(prompt) + MESSAGE_EXTRA_TOKENS;
-    }
-
     pub fn echo_messages(&self, content: &str) -> String {
-        let mut messages = self.messages.to_vec();
-        messages.push(Message {
-            role: MessageRole::User,
-            content: content.into(),
-        });
+        let messages = self.build_emssages(content);
         serde_yaml::to_string(&messages).unwrap_or("Unable to echo message".into())
     }
 
-    pub fn build_emssages(&self, content: &str) -> Value {
-        let mut messages: Vec<Value> = self.messages.iter().map(msg_to_value).collect();
-        messages.push(msg_to_value(&Message {
-            role: MessageRole::User,
-            content: content.into(),
-        }));
-        json!(messages)
+    pub fn build_emssages(&self, content: &str) -> Vec<Message> {
+        let mut messages = self.messages.to_vec();
+        let mut need_add_msg = true;
+        if messages.is_empty() {
+            if let Some(role) = self.role.as_ref() {
+                messages = role.build_emssages(content);
+                need_add_msg = false;
+            }
+        };
+        if need_add_msg {
+            messages.push(Message {
+                role: MessageRole::User,
+                content: content.into(),
+            });
+        }
+        messages
     }
 
     pub fn reamind_tokens(&self) -> usize {
         MAX_TOKENS.saturating_sub(self.tokens)
     }
 }
-
-#[derive(Debug, Clone, Deserialize, Serialize)]
-pub enum MessageRole {
-    System,
-    Assistant,
-    User,
-}
-
-impl MessageRole {
-    pub fn name(&self) -> &'static str {
-        match self {
-            MessageRole::System => "system",
-            MessageRole::Assistant => "assistant",
-            MessageRole::User => "user",
-        }
-    }
-}
-
-fn msg_to_value(msg: &Message) -> Value {
-    json!({ "role": msg.role.name(), "content": msg.content  })
-}
diff --git a/src/config/message.rs b/src/config/message.rs
new file mode 100644
index 0000000..0a06a73
--- /dev/null
+++ b/src/config/message.rs
@@ -0,0 +1,34 @@
+use serde::{Deserialize, Serialize};
+
+pub const MESSAGE_EXTRA_TOKENS: usize = 6;
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct Message {
+    pub role: MessageRole,
+    pub content: String,
+}
+
+impl Message {
+    pub fn new(content: &str) -> Self {
+        Self {
+            role: MessageRole::User,
+            content: content.to_string(),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub enum MessageRole {
+    System,
+    Assistant,
+    User,
+}
+
+#[test]
+fn test_serde() {
+    assert_eq!(
+        serde_json::to_string(&Message::new("Hello World")).unwrap(),
+        "{\"role\":\"user\",\"content\":\"Hello World\"}"
+    )
+}
diff --git a/src/config/mod.rs b/src/config/mod.rs
index 64be3bd..93168fe 100644
--- a/src/config/mod.rs
+++ b/src/config/mod.rs
@@ -1,14 +1,17 @@
 mod conversation;
+mod message;
+mod role;
 
 use self::conversation::Conversation;
+use self::message::{Message, MESSAGE_EXTRA_TOKENS};
+use self::role::Role;
 
 use crate::utils::{count_tokens, now};
 
 use anyhow::{anyhow, bail, Context, Result};
 use inquire::{Confirm, Text};
 use parking_lot::Mutex;
-use serde::{Deserialize, Serialize};
-use serde_json::{json, Value};
+use serde::Deserialize;
 use std::{
     env,
     fs::{create_dir_all, read_to_string, File, OpenOptions},
@@ -19,12 +22,10 @@ use std::{
 };
 
 const MAX_TOKENS: usize = 4096;
-const MESSAGE_EXTRA_TOKENS: usize = 6;
 const CONFIG_FILE_NAME: &str = "config.yaml";
 const ROLES_FILE_NAME: &str = "roles.yaml";
 const HISTORY_FILE_NAME: &str = "history.txt";
 const MESSAGE_FILE_NAME: &str = "messages.md";
-const TEMP_ROLE_NAME: &str = "Ｐ";
 const SET_COMPLETIONS: [&str; 9] = [
     ".set api_key",
     ".set temperature",
@@ -126,7 +127,7 @@ impl Config {
                 format!("# CHAT:[{timestamp}]\n{input}\n--------\n{output}\n--------\n\n",)
             }
             Some(v) => {
-                if v.name == TEMP_ROLE_NAME {
+                if v.is_temp() {
                     format!(
                         "# CHAT:[{timestamp}]\n{}\n{input}\n--------\n{output}\n--------\n\n",
                         v.prompt
@@ -166,7 +167,7 @@ impl Config {
         }
         match self.find_role(name) {
             Some(mut role) => {
-                role.tokens = count_tokens(&role.prompt);
+                role.tokens = role.consume_tokens();
                 let output =
                     serde_yaml::to_string(&role).unwrap_or("Unable to echo role details".into());
                 self.role = Some(role);
@@ -178,12 +179,7 @@ impl Config {
 
     pub fn create_temp_role(&mut self, prompt: &str) -> Result<()> {
         self.ensure_no_conversation()?;
-        self.role = Some(Role {
-            name: TEMP_ROLE_NAME.into(),
-            prompt: prompt.into(),
-            temperature: self.temperature,
-            tokens: count_tokens(prompt),
-        });
+        self.role = Some(Role::new(prompt, self.temperature));
         Ok(())
     }
 
@@ -198,33 +194,32 @@ impl Config {
         if let Some(conversation) = self.conversation.as_ref() {
             conversation.echo_messages(content)
         } else if let Some(role) = self.role.as_ref() {
-            format!("{}\n{content}", role.prompt)
+            role.echo_messages(content)
         } else {
             content.to_string()
         }
     }
 
-    pub fn build_messages(&self, content: &str) -> Result<Value> {
-        let tokens = count_tokens(content) + MESSAGE_EXTRA_TOKENS;
+    pub fn build_messages(&self, content: &str) -> Result<Vec<Message>> {
+        let content_tokens = count_tokens(content);
         let check_tokens = |tokens| {
             if tokens >= MAX_TOKENS {
                 bail!("Exceed max tokens limit")
             }
             Ok(())
         };
-        check_tokens(tokens)?;
-        let user_message = json!({ "role": "user", "content": content });
-        let value = if let Some(conversation) = self.conversation.as_ref() {
-            check_tokens(tokens + conversation.tokens)?;
+        let messages = if let Some(conversation) = self.conversation.as_ref() {
+            check_tokens(content_tokens + conversation.tokens)?;
             conversation.build_emssages(content)
         } else if let Some(role) = self.role.as_ref() {
-            check_tokens(tokens + role.tokens + MESSAGE_EXTRA_TOKENS)?;
-            let system_message = json!({ "role": "system", "content": role.prompt });
-            json!([system_message, user_message])
+            check_tokens(content_tokens + role.tokens)?;
+            role.build_emssages(content)
         } else {
-            json!([user_message])
+            let message = Message::new(content);
+            check_tokens(content_tokens + MESSAGE_EXTRA_TOKENS)?;
+            vec![message]
         };
-        Ok(value)
+        Ok(messages)
     }
 
     pub fn info(&self) -> Result<String> {
@@ -327,11 +322,7 @@ impl Config {
                 return Ok(());
             }
         }
-        let mut conversation = Conversation::new();
-        if let Some(role) = self.role.as_ref() {
-            conversation.add_prompt(&role.prompt);
-        }
-        self.conversation = Some(conversation);
+        self.conversation = Some(Conversation::new(self.role.clone()));
         Ok(())
     }
 
@@ -341,7 +332,7 @@ impl Config {
 
     pub fn save_conversation(&mut self, input: &str, output: &str) -> Result<()> {
         if let Some(conversation) = self.conversation.as_mut() {
-            conversation.add_chat(input, output)?;
+            conversation.add_message(input, output)?;
         }
         Ok(())
     }
@@ -376,19 +367,6 @@ impl Config {
     }
 }
 
-#[derive(Debug, Clone, Deserialize, Serialize)]
-pub struct Role {
-    /// Role name
-    pub name: String,
-    /// Prompt text send to ai for setting up a role
-    pub prompt: String,
-    /// What sampling temperature to use, between 0 and 2
-    pub temperature: Option<f64>,
-    /// Number of tokens
-    #[serde(skip_deserializing)]
-    pub tokens: usize,
-}
-
 fn create_config_file(config_path: &Path) -> Result<()> {
     let confirm_map_err = |_| anyhow!("Not finish questionnaire, try again later.");
     let text_map_err = |_| anyhow!("An error happened when asking for your key, try again later.");
diff --git a/src/config/role.rs b/src/config/role.rs
new file mode 100644
index 0000000..d0ed623
--- /dev/null
+++ b/src/config/role.rs
@@ -0,0 +1,89 @@
+use super::message::{Message, MessageRole, MESSAGE_EXTRA_TOKENS};
+
+use crate::utils::count_tokens;
+
+use serde::{Deserialize, Serialize};
+
+const TEMP_NAME: &str = "Ｐ";
+const INPUT_PLACEHOLDER: &str = "__INPUT__";
+const INPUT_PLACEHOLDER_TOKENS: usize = 3;
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct Role {
+    /// Role name
+    pub name: String,
+    /// Prompt text send to ai for setting up a role.
+    ///
+    /// If prmopt contains __INPUT___, it's embeded prompt
+    /// If prmopt don't contain __INPUT___, it's system prompt
+    pub prompt: String,
+    /// What sampling temperature to use, between 0 and 2
+    pub temperature: Option<f64>,
+    /// Number of tokens
+    ///
+    /// System prompt consume extra 6 tokens
+    #[serde(skip_deserializing)]
+    pub tokens: usize,
+}
+
+impl Role {
+    pub fn new(prompt: &str, temperature: Option<f64>) -> Self {
+        let mut value = Self {
+            name: TEMP_NAME.into(),
+            prompt: prompt.into(),
+            temperature,
+            tokens: 0,
+        };
+        value.tokens = value.consume_tokens();
+        value
+    }
+
+    pub fn is_temp(&self) -> bool {
+        self.name == TEMP_NAME
+    }
+
+    pub fn consume_tokens(&self) -> usize {
+        if self.embeded() {
+            count_tokens(&self.prompt) + MESSAGE_EXTRA_TOKENS - INPUT_PLACEHOLDER_TOKENS
+        } else {
+            count_tokens(&self.prompt) + 2 * MESSAGE_EXTRA_TOKENS
+        }
+    }
+
+    pub fn embeded(&self) -> bool {
+        self.prompt.contains(INPUT_PLACEHOLDER)
+    }
+
+    pub fn echo_messages(&self, content: &str) -> String {
+        if self.embeded() {
+            merge_prompt_content(&self.prompt, content)
+        } else {
+            format!("{}{content}", self.prompt)
+        }
+    }
+
+    pub fn build_emssages(&self, content: &str) -> Vec<Message> {
+        if self.embeded() {
+            let content = merge_prompt_content(&self.prompt, content);
+            vec![Message {
+                role: MessageRole::User,
+                content,
+            }]
+        } else {
+            vec![
+                Message {
+                    role: MessageRole::System,
+                    content: self.prompt.clone(),
+                },
+                Message {
+                    role: MessageRole::User,
+                    content: content.to_string(),
+                },
+            ]
+        }
+    }
+}
+
+pub fn merge_prompt_content(prompt: &str, content: &str) -> String {
+    prompt.replace(INPUT_PLACEHOLDER, content)
+}