use anyhow::{anyhow, Result};
use serde_json::Value;

use super::analyzer::{
    analyze_records, extract_array_at_path, find_array_paths, FieldKind, FieldProposal,
};
use crate::model::cell::{CellKey, CellValue};
use crate::model::Model;

// ── Pipeline (no UI state) ────────────────────────────────────────────────────

/// Pure data + logic for turning a JSON value into a Model.
/// No cursor, no display messages — those live in [`ImportWizard`].
#[derive(Debug)]
pub struct ImportPipeline {
    pub raw: Value,
    pub array_paths: Vec<String>,
    pub selected_path: String,
    pub records: Vec<Value>,
    pub proposals: Vec<FieldProposal>,
    pub model_name: String,
}

impl ImportPipeline {
    pub fn new(raw: Value) -> Self {
        let array_paths = find_array_paths(&raw);
        let mut pipeline = Self {
            raw: raw.clone(),
            array_paths,
            selected_path: String::new(),
            records: vec![],
            proposals: vec![],
            model_name: "Imported Model".to_string(),
        };

        // Auto-select if root is an array or there is exactly one candidate path.
        if raw.is_array() {
            pipeline.select_path("");
        } else if pipeline.array_paths.len() == 1 {
            let path = pipeline.array_paths[0].clone();
            pipeline.select_path(&path);
        }

        pipeline
    }

    pub fn select_path(&mut self, path: &str) {
        self.selected_path = path.to_string();
        if let Some(arr) = extract_array_at_path(&self.raw, path) {
            self.records = arr.clone();
            self.proposals = analyze_records(&self.records);
        }
    }

    pub fn needs_path_selection(&self) -> bool {
        self.records.is_empty() && self.raw.is_object() && self.array_paths.len() != 1
    }

    pub fn preview_summary(&self) -> String {
        match &self.raw {
            Value::Array(arr) => format!(
                "Array of {} records. Sample keys: {}",
                arr.len(),
                arr.first()
                    .and_then(|r| r.as_object())
                    .map(|m| m.keys().take(5).cloned().collect::<Vec<_>>().join(", "))
                    .unwrap_or_default()
            ),
            Value::Object(map) => format!(
                "Object with {} top-level keys: {}",
                map.len(),
                map.keys().take(10).cloned().collect::<Vec<_>>().join(", ")
            ),
            _ => "Unknown JSON structure".to_string(),
        }
    }

    /// Build a Model from the current proposals. Pure — no side effects.
    pub fn build_model(&self) -> Result<Model> {
        let categories: Vec<&FieldProposal> = self
            .proposals
            .iter()
            .filter(|p| {
                p.accepted && matches!(p.kind, FieldKind::Category | FieldKind::TimeCategory)
            })
            .collect();
        let measures: Vec<&FieldProposal> = self
            .proposals
            .iter()
            .filter(|p| p.accepted && p.kind == FieldKind::Measure)
            .collect();

        if categories.is_empty() {
            return Err(anyhow!("At least one category must be accepted"));
        }

        let mut model = Model::new(&self.model_name);

        for cat_proposal in &categories {
            model.add_category(&cat_proposal.field)?;
            if let Some(cat) = model.category_mut(&cat_proposal.field) {
                for val in &cat_proposal.distinct_values {
                    cat.add_item(val);
                }
            }
        }

        if !measures.is_empty() {
            model.add_category("Measure")?;
            if let Some(cat) = model.category_mut("Measure") {
                for m in &measures {
                    cat.add_item(&m.field);
                }
            }
        }

        for record in &self.records {
            if let Value::Object(map) = record {
                let mut coords: Vec<(String, String)> = vec![];
                let mut valid = true;

                for cat_proposal in &categories {
                    let val = map
                        .get(&cat_proposal.field)
                        .and_then(|v| v.as_str())
                        .map(|s| s.to_string())
                        .or_else(|| map.get(&cat_proposal.field).map(|v| v.to_string()));

                    if let Some(v) = val {
                        if let Some(cat) = model.category_mut(&cat_proposal.field) {
                            cat.add_item(&v);
                        }
                        coords.push((cat_proposal.field.clone(), v));
                    } else {
                        valid = false;
                        break;
                    }
                }

                if !valid {
                    continue;
                }

                for measure in &measures {
                    if let Some(val) = map.get(&measure.field).and_then(|v| v.as_f64()) {
                        let mut cell_coords = coords.clone();
                        cell_coords.push(("Measure".to_string(), measure.field.clone()));
                        model.set_cell(CellKey::new(cell_coords), CellValue::Number(val));
                    }
                }
            }
        }

        Ok(model)
    }
}

// ── Wizard (UI state wrapped around the pipeline) ─────────────────────────────

#[derive(Debug, Clone, PartialEq)]
pub enum WizardStep {
    Preview,
    SelectArrayPath,
    ReviewProposals,
    NameModel,
    Done,
}

/// Interactive state layered on top of [`ImportPipeline`] for the TUI wizard.
/// The pipeline holds all data; the wizard holds only what the UI needs to
/// drive the multi-step interaction (current step, list cursor, error message).
#[derive(Debug)]
pub struct ImportWizard {
    pub pipeline: ImportPipeline,
    pub step: WizardStep,
    /// Cursor within the current list (array paths or proposals).
    pub cursor: usize,
    /// One-line message to display at the bottom of the wizard panel.
    pub message: Option<String>,
}

impl ImportWizard {
    pub fn new(raw: Value) -> Self {
        let pipeline = ImportPipeline::new(raw);

        let step = if pipeline.needs_path_selection() {
            WizardStep::SelectArrayPath
        } else if pipeline.records.is_empty() {
            WizardStep::Preview
        } else {
            WizardStep::ReviewProposals
        };

        Self {
            pipeline,
            step,
            cursor: 0,
            message: None,
        }
    }

    // ── Step transitions ──────────────────────────────────────────────────────

    pub fn advance(&mut self) {
        self.step = match self.step {
            WizardStep::Preview => {
                if self.pipeline.array_paths.len() > 1 && self.pipeline.needs_path_selection() {
                    WizardStep::SelectArrayPath
                } else {
                    WizardStep::ReviewProposals
                }
            }
            WizardStep::SelectArrayPath => WizardStep::ReviewProposals,
            WizardStep::ReviewProposals => WizardStep::NameModel,
            WizardStep::NameModel => WizardStep::Done,
            WizardStep::Done => WizardStep::Done,
        };
        self.cursor = 0;
        self.message = None;
    }

    pub fn confirm_path(&mut self) {
        if self.cursor < self.pipeline.array_paths.len() {
            let path = self.pipeline.array_paths[self.cursor].clone();
            self.pipeline.select_path(&path);
            self.advance();
        }
    }

    // ── Cursor movement ───────────────────────────────────────────────────────

    pub fn move_cursor(&mut self, delta: i32) {
        let len = match self.step {
            WizardStep::SelectArrayPath => self.pipeline.array_paths.len(),
            WizardStep::ReviewProposals => self.pipeline.proposals.len(),
            _ => 0,
        };
        if len == 0 {
            return;
        }
        if delta > 0 {
            self.cursor = (self.cursor + 1).min(len - 1);
        } else if self.cursor > 0 {
            self.cursor -= 1;
        }
    }

    // ── Proposal editing (delegates to pipeline) ──────────────────────────────

    pub fn toggle_proposal(&mut self) {
        if self.cursor < self.pipeline.proposals.len() {
            self.pipeline.proposals[self.cursor].accepted =
                !self.pipeline.proposals[self.cursor].accepted;
        }
    }

    pub fn cycle_proposal_kind(&mut self) {
        if self.cursor < self.pipeline.proposals.len() {
            let p = &mut self.pipeline.proposals[self.cursor];
            p.kind = match p.kind {
                FieldKind::Category => FieldKind::Measure,
                FieldKind::Measure => FieldKind::TimeCategory,
                FieldKind::TimeCategory => FieldKind::Label,
                FieldKind::Label => FieldKind::Category,
            };
        }
    }

    // ── Model name input ──────────────────────────────────────────────────────

    pub fn push_name_char(&mut self, c: char) {
        self.pipeline.model_name.push(c);
    }
    pub fn pop_name_char(&mut self) {
        self.pipeline.model_name.pop();
    }

    // ── Delegate build to pipeline ────────────────────────────────────────────

    pub fn build_model(&self) -> Result<Model> {
        self.pipeline.build_model()
    }
}

#[cfg(test)]
mod tests {
    use super::ImportPipeline;
    use crate::import::analyzer::FieldKind;
    use serde_json::json;

    #[test]
    fn flat_array_auto_selected() {
        let raw = json!([
            {"region": "East", "product": "Shirts", "revenue": 100.0},
            {"region": "West", "product": "Shirts", "revenue": 200.0},
        ]);
        let p = ImportPipeline::new(raw);
        assert!(!p.records.is_empty());
        assert!(!p.proposals.is_empty());
        assert!(!p.needs_path_selection());
    }

    #[test]
    fn numeric_field_proposed_as_measure() {
        let raw = json!([{"region": "East", "revenue": 100.0, "cost": 50.0}]);
        let p = ImportPipeline::new(raw);
        let revenue = p.proposals.iter().find(|p| p.field == "revenue").unwrap();
        assert_eq!(revenue.kind, FieldKind::Measure);
    }

    #[test]
    fn low_cardinality_string_field_proposed_as_category() {
        let raw = json!([
            {"region": "East", "revenue": 100.0},
            {"region": "West", "revenue": 200.0},
            {"region": "East", "revenue": 150.0},
        ]);
        let p = ImportPipeline::new(raw);
        let region = p.proposals.iter().find(|p| p.field == "region").unwrap();
        assert_eq!(region.kind, FieldKind::Category);
    }

    #[test]
    fn nested_json_needs_path_selection_when_multiple_arrays() {
        let raw = json!({
            "orders":   [{"id": 1}, {"id": 2}],
            "products": [{"name": "A"}, {"name": "B"}],
        });
        let p = ImportPipeline::new(raw);
        assert!(p.needs_path_selection());
    }

    #[test]
    fn single_nested_array_auto_selected() {
        let raw = json!({
            "data": [
                {"region": "East", "revenue": 100.0},
                {"region": "West", "revenue": 200.0},
            ]
        });
        let p = ImportPipeline::new(raw);
        assert!(!p.records.is_empty());
        assert!(!p.needs_path_selection());
    }

    #[test]
    fn select_path_populates_records_and_proposals() {
        let raw = json!({
            "a": [{"x": 1}, {"x": 2}],
            "b": [{"y": "foo"}, {"y": "bar"}],
        });
        let mut p = ImportPipeline::new(raw);
        p.select_path("b");
        assert!(!p.records.is_empty());
        assert!(!p.proposals.is_empty());
    }

    #[test]
    fn build_model_fails_with_no_accepted_categories() {
        let raw = json!([{"revenue": 100.0, "cost": 50.0}]);
        let mut p = ImportPipeline::new(raw);
        for prop in &mut p.proposals {
            prop.accepted = false;
        }
        assert!(p.build_model().is_err());
    }

    #[test]
    fn build_model_creates_categories_and_measure_category() {
        let raw = json!([
            {"region": "East", "revenue": 100.0},
            {"region": "West", "revenue": 200.0},
        ]);
        let p = ImportPipeline::new(raw);
        let model = p.build_model().unwrap();
        assert!(model.category("region").is_some());
        assert!(model.category("Measure").is_some());
    }

    #[test]
    fn build_model_cells_match_source_data() {
        let raw = json!([
            {"region": "East", "revenue": 100.0},
            {"region": "West", "revenue": 200.0},
        ]);
        let p = ImportPipeline::new(raw);
        let model = p.build_model().unwrap();
        use crate::model::cell::CellKey;
        let k_east = CellKey::new(vec![
            ("Measure".to_string(), "revenue".to_string()),
            ("region".to_string(), "East".to_string()),
        ]);
        let k_west = CellKey::new(vec![
            ("Measure".to_string(), "revenue".to_string()),
            ("region".to_string(), "West".to_string()),
        ]);
        assert_eq!(
            model.get_cell(&k_east).and_then(|v| v.as_f64()),
            Some(100.0)
        );
        assert_eq!(
            model.get_cell(&k_west).and_then(|v| v.as_f64()),
            Some(200.0)
        );
    }

    #[test]
    fn model_name_defaults_to_imported_model() {
        let raw = json!([{"x": 1.0}]);
        let p = ImportPipeline::new(raw);
        assert_eq!(p.model_name, "Imported Model");
    }
}