use crate::*;

/// A template expander owning the value you set
/// so that you don't have to keep them around until
/// you produce the text to display.
/// Additionnaly, the same expander can be used for several
/// templates.
#[derive(Default)]
pub struct OwningTemplateExpander<'s> {
    ops: Vec<FillingOperation<'s>>,
    default_value: Option<String>,
}
#[derive(Default)]
pub struct OwningSubTemplateExpander<'s> {
    ops: Vec<SubFillingOperation<'s>>,
}

enum FillingOperation<'s> {
    Set {
        name: &'s str,
        value: String,
    },
    SetMD {
        name: &'s str,
        value: String,
    },
    SetLines {
        name: &'s str,
        value: String,
    },
    SetLinesMD {
        name: &'s str,
        value: String,
    },
    Sub {
        name: &'s str,
        sub_expander: OwningSubTemplateExpander<'s>,
    },
}
enum SubFillingOperation<'s> {
    Set { name: &'s str, value: String },
    SetMD { name: &'s str, value: String },
}

impl<'s> OwningTemplateExpander<'s> {
    pub fn new() -> Self {
        Self::default()
    }

    /// set a default value to use when no replacement was defined.
    /// When you don't call this method, the expanded text contains the
    /// original names like `${my_arg_name}` (which is useful when developing
    /// your filling code)
    pub fn set_default<S: Into<String>>(
        &mut self,
        value: S,
    ) -> &mut Self {
        self.default_value = Some(value.into());
        self
    }

    /// replace placeholders with name `name` with the given value, non interpreted
    /// (i.e. stars, backquotes, etc. don't mess the styling defined by the template)
    pub fn set<S: std::fmt::Display>(
        &mut self,
        name: &'s str,
        value: S,
    ) -> &mut Self {
        self.ops.push(FillingOperation::Set {
            name,
            value: value.to_string(),
        });
        self
    }

    /// replace placeholders with name `name` with the given value, interpreted as markdown
    pub fn set_md<S: Into<String>>(
        &mut self,
        name: &'s str,
        value: S,
    ) -> &mut Self {
        self.ops.push(FillingOperation::SetMD {
            name,
            value: value.into(),
        });
        self
    }

    /// return a sub template expander. You can do set and `set_md`
    /// on the returned sub to fill an instance of the repeation section.
    pub fn sub(
        &mut self,
        name: &'s str,
    ) -> &mut OwningSubTemplateExpander<'s> {
        let idx = self.ops.len();
        self.ops.push(FillingOperation::Sub {
            name,
            sub_expander: OwningSubTemplateExpander::new(),
        });
        match &mut self.ops[idx] {
            FillingOperation::Sub {
                name: _,
                sub_expander,
            } => sub_expander,
            _ => unreachable!(),
        }
    }

    /// replace a placeholder with several lines.
    /// This is mostly useful when the placeholder is a repeatable line (code, list item)
    pub fn set_lines<S: Into<String>>(
        &mut self,
        name: &'s str,
        raw_lines: S,
    ) -> &mut Self {
        self.ops.push(FillingOperation::SetLines {
            name,
            value: raw_lines.into(),
        });
        self
    }

    /// replace a placeholder with several lines interpreted as markdown
    pub fn set_lines_md<S: Into<String>>(
        &mut self,
        name: &'s str,
        md: S,
    ) -> &mut Self {
        self.ops.push(FillingOperation::SetLinesMD {
            name,
            value: md.into(),
        });
        self
    }

    /// build a text by applying the replacements to the initial template
    pub fn expand<'t>(
        &'s self,
        template: &'t TextTemplate<'s>,
    ) -> Text<'s> {
        let mut expander = template.expander();
        if let Some(s) = &self.default_value {
            expander.set_all(s);
        }
        for op in &self.ops {
            match op {
                FillingOperation::Set { name, value } => {
                    expander.set(name, value);
                }
                FillingOperation::SetMD { name, value } => {
                    expander.set_md(name, value);
                }
                FillingOperation::SetLines { name, value } => {
                    expander.set_lines(name, value);
                }
                FillingOperation::SetLinesMD { name, value } => {
                    expander.set_lines_md(name, value);
                }
                FillingOperation::Sub { name, sub_expander } => {
                    let sub = expander.sub(name);
                    for op in &sub_expander.ops {
                        match op {
                            SubFillingOperation::Set { name, value } => {
                                sub.set(name, value);
                            }
                            SubFillingOperation::SetMD { name, value } => {
                                sub.set_md(name, value);
                            }
                        }
                    }
                }
            }
        }
        expander.expand()
    }
}

impl<'s> OwningSubTemplateExpander<'s> {
    pub fn new() -> Self {
        Self { ops: Vec::new() }
    }
    /// replace placeholders with name `name` with the given value, non interpreted
    /// (i.e. stars, backquotes, etc. don't mess the styling defined by the template)
    pub fn set<S: std::fmt::Display>(
        &mut self,
        name: &'s str,
        value: S,
    ) -> &mut Self {
        self.ops.push(SubFillingOperation::Set {
            name,
            value: value.to_string(),
        });
        self
    }

    pub fn set_option<S: std::fmt::Display>(
        &mut self,
        name: &'s str,
        value: Option<S>,
    ) -> &mut Self {
        if let Some(value) = value {
            self.ops.push(SubFillingOperation::Set {
                name,
                value: value.to_string(),
            });
        }
        self
    }

    /// replace placeholders with name `name` with the given value, interpreted as markdown
    pub fn set_md<S: Into<String>>(
        &mut self,
        name: &'s str,
        value: S,
    ) -> &mut Self {
        self.ops.push(SubFillingOperation::SetMD {
            name,
            value: value.into(),
        });
        self
    }
}
