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.
```

1 files changed, 89 insertions, 0 deletions

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)
+}