added chapter 3 code
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# This file is automatically @generated by Cargo.
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# It is not intended for manual editing.
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[[package]]
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name = "template-engine"
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version = "0.1.0"
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[package]
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name = "template-engine"
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version = "0.1.0"
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authors = ["peshwar9 <par.esh1937@gmail.com>"]
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edition = "2018"
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# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
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[dependencies]
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// Standard library imports
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use std::collections::HashMap;
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// Each line in template file can be of one of following types
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#[derive(PartialEq, Debug)]
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pub enum ContentType {
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Literal(String),
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TemplateVariable(ExpressionData),
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Tag(TagType),
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Unrecognized,
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}
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//IF ContentType is TemplateVariable, the contents of the line are parsed and stored in the ExpressionData struct.alloc
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// If template file contains this line: <p> Hello {{name}} ,welcome </p> then
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// Head = "Hello" , variable = "name" and tail = ",welcome"
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#[derive(PartialEq, Debug)]
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pub struct ExpressionData {
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pub head: Option<String>,
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pub variable: String,
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pub tail: Option<String>,
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}
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#[derive(PartialEq, Debug)]
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pub enum TagType {
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ForTag,
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IfTag,
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}
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//this checks if a symbol string is contained within another string
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pub fn check_symbol_string(input: &str, symbol: &str) -> bool {
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let symbols = input.chars();
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symbols.as_str().contains(symbol)
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}
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// This checks for matching symbol strings in a given input
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pub fn check_matching_pair(input: &str, symbol1: &str, symbol2: &str) -> bool {
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let input_iter = input.chars();
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input_iter.as_str().contains(symbol1) && input_iter.as_str().contains(symbol2)
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}
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// this returns index of given char symbol, if symbol is present.
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pub fn get_index_for_symbol(input: &str, symbol: char) -> (bool, usize) {
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let mut characters = input.char_indices();
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let mut does_exist = false;
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let mut index = 0;
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while let Some((c, d)) = characters.next() {
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if d == symbol {
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does_exist = true;
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index = c;
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break;
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}
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}
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(does_exist, index)
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}
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// Reads one line of template file and returns type of Content. The types of content are defined in ContentType enum
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// If contentType is TemplateVariable, it parses the line further to separate out the head, variable and tail components.
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// IF ContentType is Literal, it returns the read input without any modifications.
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pub fn get_content_type(input_line: &str) -> ContentType {
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// Tag expressions are enclosed within {% and %}
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let is_tag_expression = check_matching_pair(&input_line, "{%", "%}");
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// ForTag expressions begin with keywords 'for' and 'in' enclosed within {% and %}
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// ForTag expressions end with keyword 'endfor' enclosed within {% and %}
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let is_for_tag = (check_symbol_string(&input_line, "for")
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&& check_symbol_string(&input_line, "in"))
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|| check_symbol_string(&input_line, "endfor");
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// IfTag expressions begin with keyword 'if' enclosed within {% and %}
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// IfTag expressions end with keyword 'endif' enclosed within {% and %}
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let is_if_tag =
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check_symbol_string(&input_line, "if") || check_symbol_string(&input_line, "endif");
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// Template variables have
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// 1) an optional head,
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// 2) a template variable enclosed within {{ and }}
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// 3) an optional tail
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// eg the expression <p> Hello {{name}} ,welcome </p> is parsed as follows:
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// head = 'Hello', variable = 'name' and tail = ',welcome'
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let is_template_variable = check_matching_pair(&input_line, "{{", "}}");
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let return_val;
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// case: For Tag
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if is_tag_expression && is_for_tag {
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return_val = ContentType::Tag(TagType::ForTag);
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//case: If Tag
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} else if is_tag_expression && is_if_tag {
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return_val = ContentType::Tag(TagType::IfTag);
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// case: Template variable
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} else if is_template_variable {
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let content = get_expression_data(&input_line);
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return_val = ContentType::TemplateVariable(content);
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// case: Literal
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} else if !is_tag_expression && !is_template_variable {
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return_val = ContentType::Literal(input_line.to_string());
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// Unknown type
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} else {
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return_val = ContentType::Unrecognized;
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}
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return_val
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}
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// Function to generate HTML for line containing template variable
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pub fn generate_html_template_var(
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content: ExpressionData,
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context: HashMap<String, String>,
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) -> String {
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let mut html = String::new();
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if let Some(h) = content.head {
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html.push_str(&h);
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}
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if let Some(val) = context.get(&content.variable) {
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html.push_str(&val);
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}
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if let Some(t) = content.tail {
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html.push_str(&t);
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}
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html
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}
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// Helper function to parse template variable
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pub fn get_expression_data(input_line: &str) -> ExpressionData {
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let (_h, i) = get_index_for_symbol(input_line, '{');
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let head = input_line[0..i].to_string();
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let (_j, k) = get_index_for_symbol(input_line, '}');
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let variable = input_line[i + 1 + 1..k].to_string();
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let tail = input_line[k + 1 + 1..].to_string();
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ExpressionData {
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head: Some(head),
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variable: variable,
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tail: Some(tail),
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}
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}
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//Unit tests
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn check_get_index_for_symbol_test() {
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assert_eq!((true, 3), get_index_for_symbol("Hi {name} bye", '{'));
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}
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#[test]
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fn check_template_var_test() {
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let content = ExpressionData {
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head: Some("Hi ".to_string()),
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variable: "name".to_string(),
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tail: Some(" bye".to_string()),
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};
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assert_eq!(
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ContentType::TemplateVariable(content),
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get_content_type("Hi {{name}} bye")
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);
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}
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#[test]
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fn check_for_tag_test() {
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assert_eq!(
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ContentType::Tag(TagType::ForTag),
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get_content_type("{% for name in names %} bye")
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);
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}
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#[test]
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fn check_if_tag_test() {
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assert_eq!(
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ContentType::Tag(TagType::IfTag),
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get_content_type("{% if name == 'Bob' %}")
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);
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}
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#[test]
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fn check_literal_test() {
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let s = "<h1>Hello world</h1>";
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assert_eq!(ContentType::Literal(s.to_string()), get_content_type(s));
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}
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#[test]
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fn check_get_expression_data_test() {
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let expression_data = ExpressionData {
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head: Some("Hi ".to_string()),
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variable: "name".to_string(),
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tail: Some(",welcome".to_string()),
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};
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assert_eq!(expression_data, get_expression_data("Hi {{name}},welcome"));
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}
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#[test]
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fn check_symbol_string_test() {
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assert_eq!(true, check_symbol_string("{{Hello}}", "{{"));
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}
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#[test]
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fn check_symbol_pair_test() {
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assert_eq!(true, check_matching_pair("{{Hello}}", "{{", "}}"));
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}
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}
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use std::collections::HashMap;
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use std::io;
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use std::io::BufRead;
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use template_engine::*;
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fn main() {
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let mut context: HashMap<String, String> = HashMap::new();
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context.insert("name".to_string(), "Bob".to_string());
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context.insert("city".to_string(), "Boston".to_string());
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for line in io::stdin().lock().lines() {
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match get_content_type(&line.unwrap().clone()) {
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ContentType::TemplateVariable(content) => {
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let html = generate_html_template_var(content, context.clone());
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println!("{}", html);
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}
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ContentType::Literal(text) => println!("{}", text),
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ContentType::Tag(TagType::ForTag) => println!("For Tag not implemented"),
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ContentType::Tag(TagType::IfTag) => println!("If Tag not implemented"),
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ContentType::Unrecognized => println!("Unrecognized input"),
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}
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}
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}
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