//! Column configuration for table mode. Defines which fields
//! to display as columns and how to label them.

use crate::item::resolve_field_path;
use serde_json::Value;

/// A single column definition: which field to extract and
/// what to call it in the header.
#[derive(Debug, Clone)]
pub struct ColumnDef {
    /// Dotted path into the item's JSON value (e.g. "meta.res").
    pub field: String,
    /// Display name for the column header. Defaults to the
    /// field path if no alias is given.
    pub display_name: String,
}

/// Column layout for table mode. Controls which fields are
/// shown and in what order.
#[derive(Debug, Clone)]
pub struct ColumnConfig {
    pub columns: Vec<ColumnDef>,
}

impl ColumnConfig {
    /// Parse a column spec string like "label,meta.res:Resolution,meta.size".
    /// Columns are comma-separated. Each column can have an alias
    /// after the first colon: "field:Alias".
    pub fn parse(spec: &str) -> Self {
        let columns = spec
            .split(',')
            .filter(|s| !s.is_empty())
            .map(|part| {
                let part = part.trim();
                if let Some((field, alias)) = part.split_once(':') {
                    ColumnDef {
                        field: field.trim().to_string(),
                        display_name: alias.trim().to_string(),
                    }
                } else {
                    ColumnDef {
                        field: part.to_string(),
                        display_name: part.to_string(),
                    }
                }
            })
            .collect();
        Self { columns }
    }

    /// Build a ColumnConfig from raw header names. Used when
    /// auto-generating columns from CSV headers.
    pub fn from_headers(headers: &[String]) -> Self {
        let columns = headers
            .iter()
            .map(|h| ColumnDef {
                field: h.clone(),
                display_name: h.clone(),
            })
            .collect();
        Self { columns }
    }

    /// Resolve each column's value from an item's JSON value.
    /// Missing fields produce an empty string.
    pub fn resolve_values(&self, value: &Value) -> Vec<String> {
        self.columns
            .iter()
            .map(|col| {
                resolve_field_path(value, &col.field)
                    .map(value_to_cell)
                    .unwrap_or_default()
            })
            .collect()
    }
}

/// Convert a JSON value to a cell string for display.
fn value_to_cell(v: &Value) -> String {
    match v {
        Value::String(s) => s.clone(),
        Value::Number(n) => n.to_string(),
        Value::Bool(b) => b.to_string(),
        Value::Null => String::new(),
        other => other.to_string(),
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use serde_json::json;

    #[test]
    fn parse_simple_columns() {
        let config = ColumnConfig::parse("label,age,city");
        assert_eq!(config.columns.len(), 3);
        assert_eq!(config.columns[0].field, "label");
        assert_eq!(config.columns[0].display_name, "label");
        assert_eq!(config.columns[2].field, "city");
    }

    #[test]
    fn parse_with_alias() {
        let config = ColumnConfig::parse("label,meta.res:Resolution");
        assert_eq!(config.columns.len(), 2);
        assert_eq!(config.columns[1].field, "meta.res");
        assert_eq!(config.columns[1].display_name, "Resolution");
    }

    #[test]
    fn parse_empty_string() {
        let config = ColumnConfig::parse("");
        assert!(config.columns.is_empty());
    }

    #[test]
    fn parse_trailing_comma() {
        let config = ColumnConfig::parse("label,age,");
        assert_eq!(config.columns.len(), 2);
    }

    #[test]
    fn resolve_flat_values() {
        let config = ColumnConfig::parse("label,age");
        let value = json!({"label": "alice", "age": 30});
        let cells = config.resolve_values(&value);
        assert_eq!(cells, vec!["alice", "30"]);
    }

    #[test]
    fn resolve_nested_values() {
        let config = ColumnConfig::parse("label,meta.res");
        let value = json!({"label": "test", "meta": {"res": "1080p"}});
        let cells = config.resolve_values(&value);
        assert_eq!(cells, vec!["test", "1080p"]);
    }

    #[test]
    fn resolve_missing_field() {
        let config = ColumnConfig::parse("label,nope");
        let value = json!({"label": "test"});
        let cells = config.resolve_values(&value);
        assert_eq!(cells, vec!["test", ""]);
    }

    #[test]
    fn from_headers_builds_identity() {
        let headers = vec!["name".to_string(), "age".to_string()];
        let config = ColumnConfig::from_headers(&headers);
        assert_eq!(config.columns.len(), 2);
        assert_eq!(config.columns[0].field, "name");
        assert_eq!(config.columns[0].display_name, "name");
    }
}